February 14, 2013
It’s obvious that anti-anxiety medicines and other types of mood-modifying drugs alter the behavior of humans—it’s what they’re designed to do. But their effects, it turns out, aren’t limited to our species.
Over the past decade, researchers have repeatedly discovered high levels of many drug molecules in lakes and streams near wastewater treatment plants, and found evidence that rainbow trout and other fish subjected to these levels could absorb dangerous amounts of the medications over time. Now, a study published today in Science finds a link between behavior-modifying drugs and the actual behavior of fish for the first time. A group of researchers from Umeå University in Sweden found that levels of the anti-anxiety drug oxazepam commonly found in Swedish streams cause wild perch to act differently, becoming more anti-social, eating faster and showing less fear of unknown parts of their environment.
The research group, led by ecologist Tomas Brodin, put wild perch in water with 1.8 micrograms of oxazepam diluted per liter—a level consistent with samples taken from surface waters near human development around Sweden. After 7 days swimming in the contaminated water, the perch had levels of the drug in their tissues that were similar to those of wild perch samples, indicating that the pharmaceutical was being absorbed into their bodies at rates similar to what’s happening in rivers and streams.
When they closely observed the behavior of these contaminated fish, the results were unmistakable. Those dosed with the anti-anxiety drug were more active, more willing to explore novel parts of their environment and more likely to swim away from the rest of their group as compared to fish that were kept in pristine waters. They also ate faster, finishing a set amount of plankton in a shorter time.
The researchers also included a third group of fish, exposed to levels of the drug way higher than those present in the environment. All of the changes shown in the fish exposed to the mild level of the drug were greatly exaggerated in this group, indicating that the drug was indeed responsible for the behavioral changes observed.
The idea of drug-addled fish might be funny, but the researchers say it could be a troubling sign of the way mounting levels of water-borne pharmaceuticals are affecting natural ecosystems. Because perch and other predator fish play a key role in food webs, altered foraging behavior—say, eating more prey—could lead to proliferation of the algae that their prey typically eat, upsetting an ecosystem’s balance as a whole. Or, if wild perch are engaging in more risky behavior (exploring parts of their environment they usually shy away from) it could lower the species’ survival rate.
Additionally, the research group worries that the drug could affect a broad spectrum of wildlife, because the particular receptor it binds to in the brain is widely distributed among aquatic species. And Oxazepam is far from the only drug that’s been found to pollute aquatic ecosystems—in the U.S., traces of over-the-counter painkillers, birth control hormones and illegal drugs have all been detected. “That environmentally relevant concentrations of a single benzodiazepine [oxazepam] affect fish behavior and feeding rate is alarming, considering the cocktail of different pharmaceutical products that are found in waters worldwide,” the researchers note in the paper.
These drug molecules can enter the environment in a few different ways. The practice of flushing old pills down the toilet is the first that probably comes to mind—and the easiest to prevent—but many pharmaceutical pollutants result from drug molecules that are ingested properly, go through the human body, pass out in urine and make it through wastewater treatment plants and into the environment. ”The solution to this problem isn’t to stop medicating people who are ill but to try to develop sewage treatment plants that can capture environmentally hazardous drugs,” Jerker Fick, one of the paper’s co-authors, said in a statement.
February 13, 2013
Even in the utterly dry language of science, there is no way to describe the mating behavior of the sea slug Chromodoris reticulata as anything other than bizarre. The creature, native to the Pacific Ocean, engages in simultaneous hermaphroditic mating—that is, each slug has both a penis and a vagina, and when mating, both members of a couple inserts their penises into the other’s vagina at the same time—but that’s not nearly the strangest aspect of their reproduction efforts.
As discovered by a group of Japanese scientists and revealed today in the journal Biology Letters, it’s what C. reticulata does after sex that is particularly unexpected—and previously unknown in the animal kingdom. After copulating for about 10 minutes, each slug discards its penis and immediately begins growing a new one, which is ready for use within 24 hours.
The research team, led by Ayami Sekizawa of Osaka City University, gathered a number of specimens from coral reefs off of Okinawa and observed their mating behavior in lab tanks. They found that the slugs typically mated for roughly 10 minutes—with each member of a couple assuming both the female and male roles simultaneously—then disengaged, wherein their penises fell off and floated free in the water.
Within roughly 24 hours, the slugs’ penises grew back and they were able to mate once again. If they put a slug in a tank with another before that period had elapsed, it either served just a female role during copulation or avoided mating entirely.
With a full day for regeneration, though, their mating behavior was entirely regular. One particularly vigorous specimen was even able to grow its penis back twice in a row, mating 3 times consecutively with 24 hours between each instance.
The physiology that allows the slug to achieve this feat is fascinating in itself. The researchers observed that the animal’s vas deferens—the coiled internal duct that transports sperm outward—serves as a sort of “next penis” (their phrasing), extending out of the body to replace the old discarded penis.
Why would an organism go to the trouble of regenerating a new penis each time it mates? The scientists speculate that the strange behavior could be an evolutionary response to competition among mates.
The tips of the slugs’ penises, it turns out, are covered with microscopic barbs that were observed to be coated with sperm after mating. This might not be the particular slug’s sperm, the researchers theorize, but a competitor’s—and the barbs might exist to remove sperm deposited by previous slugs in their mates’ vaginas, thereby increasing the chance that it’s their sperm that leads to reproduction. Afterwards, instead of retaining a penis covered in a competitor’s sperm, it’s simpler to discard it and grow a new one.
So no matter how difficult your romantic trials and tribulations, it’s worth remembering: We still have it quite a bit easier than C. reticulata.
January 18, 2013
It’s conventional wisdom that three things in life are inevitable: death, taxes and smelly armpits. But the third trouble on that list, it turns out, only afflicts 98% of us. According to a group of researchers from the University of Bristol in the UK, 2 percent of people (at least in their survey) carry a rare version of the gene ABCC11 that prevents their armpits from producing an offensive odor.
The study, published yesterday in the Journal of Investigative Dermatology, examined 6,495 British mothers who have been part of a longitudinal health study since they gave birth in either 1991 or 1992. About 2 percent—117 mothers, to be exact—had the gene, according to DNA analysis.
Researchers have apparently known that this gene exists for some time, although most work on it has focused on its connection to earwax: People with the rare gene variant are more likely to have “dry” earwax (as opposed to wet or sticky). Thus, one way to try figuring out if you’ve been blessed with stink-free armpits is to consider whether your earwax is uncommonly dry. It’s also been discovered that the non-stinky gene is more common in East Asian populations.
Researchers still aren’t sure how the gene affects both earwax and sweat odor, but they believe it has to do with amino acid production. Rapidly growing bacteria give sweat its smelliness, and people with the rare gene variant appear to produce less of an animo acid that engenders bacteria growth.
This particular study examined just how many of these remarkable individuals still wear deodorant despite their lucky genetic inheritance. Whether they knew that they carried the gene or not, people with the trait were less likely to wear deodorant or antiperspirant: 78% reported wearing it on all or most days, versus 95% of the others in the study. At some point in their lives, a decent proportion must have figured out that they really don’t need to wear these sorts of products to avoid stinking.
Still, most of the people with the gene wake up everyday and apply deodorant, a trend the researchers chalk up to socio-cultural norms. They think their findings could save these people a little money and trouble and let them skip deodorant entirely.
“These findings have some potential for using genetics in the choice of personal hygiene products,” Santio Rodriguez, the lead author, said in a statement. “A simple gene test might strengthen self-awareness and save some unnecessary purchases and chemical exposures for non-odour producers.”
A noble cause, indeed. We have just one suggestion: You may want to confirm you have the gene before leaving the house au naturale.
January 15, 2013
For years, when museums, textbooks or other outlets attempted to illustrate what a particular ancient human skeleton would have looked like in the flesh, their method was admittedly unscientific—they basically had to make an educated guess.
Now, though, a group of researchers from Poland and the Netherlands has provided a remarkable new option, described in an article they published in the journal Investigative Genetics on Sunday. By adapting DNA analysis methods originally developed for forensic investigations, they’ve been able to determine the hair and eye color of humans who lived as long as 800 years ago.
The team’s method examines 24 locations in the human genome that vary between individuals and play a role in determining hair and eye color. Although this DNA degrades over time, the system is sensitive enough to generate this information from genetic samples—taken either from teeth or bones—that are several centuries old (although the most degraded samples can provide information for eye color only).
As a proof of concept, the team performed the analysis for a number of people whose eye and hair color we already know. Among others, they tested the DNA of Władysław Sikorski, a former Prime Minister of Poland who died in a 1943 plane crash, and determined that Sikorski had blue eyes and blonde hair, which correctly matches color photographs.
But the more useful application of the new method is providing new information. “This system can be used to solve historical controversies where colour photographs or other records are missing,” co-author Manfred Kayser, of Erasmus University in Rotterdam, said in a statement.
For example, in the paper, the researchers analyzed the hair and eye color for a female skeleton buried in the crypt of a Benedictine Abbey near Kraków, Poland, sometime between the 12th and 14th centuries. The skeleton had been of interest to archaeologists for some time, since male monks were typically the only people buried in the crypt. The team’s analysis showed that she had brown eyes and dark blond or brown hair.
The team is not sure yet just how old a skeleton has to be for its DNA to be degraded beyond use—the woman buried in the crypt was the oldest one tested—so it‘s conceivable that it might even work for individuals who’ve been in the ground for more than a millenium. The researchers suggest this sort of analysis could soon become part of a standard anthropological toolkit for evaluating human remains.
December 20, 2012
One of the chief arguments for the legalization of medicinal marijuana is its usefulness as a pain reliever. For many cancer and AIDS patients across the 19 states where medicinal use of the drug has been legalized, it has proven to be a valuable tool in managing chronic pain—in some cases working for patients for which conventional painkillers are ineffective.
To determine exactly how cannabis relieves pain, a group of Oxford researchers used healthy volunteers, an MRI machine and doses of THC, the active ingredient in marijuana. Their findings, published today in the journal Pain, suggest something counterintuitive: that the drug doesn’t so much reduce pain as make the same level of pain more bearable.
“Cannabis does not seem to act like a conventional pain medicine,” Michael Lee, an Oxford neuroscientist and lead author of the paper, said in a statement. “Brain imaging shows little reduction in the brain regions that code for the sensation of pain, which is what we tend to see with drugs like opiates. Instead, cannabis appears to mainly affect the emotional reaction to pain in a highly variable way.”
As part of the study, Lee and colleagues recruited 12 healthy volunteers who said they’d never used marijuana before and gave each one either a THC tablet or a placebo. Then, to trigger a consistent level of pain, they rubbed a cream on the volunteers’ legs that included 1% capsaicin, the compound found that makes chili peppers spicy; in this case, it caused a burning sensation on the skin.
When the researchers asked each person to report both the intensity and the unpleasantness of the pain—in other words, how much it physically burned and how much this level of burning bothered them—they came to the surprising finding. “We found that with THC, on average people didn’t report any change in the burn, but the pain bothered them less,” Lee said.
This indicates that marijuana doesn’t function as a pain killer as much as a pain distracter: Objectively, levels of pain remain the same for someone under the influence of THC, but it simply bothers the person less. It’s difficult to draw especially broad conclusions from a study with a sample size of just 12 participants, but the results were still surprising.
Each of the participants was also put in an MRI machine—so the researchers could try to pinpoint which areas of the brain seemed to be involved in THC’s pain relieving processes—and the results backed up the theory. Changes in brain activity due to THC involved areas such as the anterior mid-cingulate cortex, believed to be involved in the emotional aspects of pain, rather than other areas implicated in the direct physical perception of it.
Additionally, the researchers found that THC’s effectiveness in reducing the unpleasantness of pain varied greatly between individuals—another characteristic that sets it apart from typical painkillers. For some participants, it made the capsaicin cream much less bothersome, while for others, it had little effect.
The MRI scans supported this observation, too: Those more affected by the THC demonstrated more brain activity connecting their right amydala and a part of the cortex known as the primary sensorimotor area. The researchers say that this finding could perhaps be used as a diagnostic tool, indicating for which patients THC could be most effective as a pain treatment medicine.