Science and Medicine

Scientists Discover How Chemical Repellants Trip Up Insects



Fire up the citronella-scented tiki torches, and slather on the DEET: Everybody knows these simple precautions repel insects, notably mosquitoes, whose bites not only itch and irritate, but also transmit diseases such as West Nile virus, malaria and dengue.

Fire up the citronella-scented tiki torches, and slather on the DEET: Everybody knows these simple precautions repel insects, notably mosquitoes, whose bites not only itch and irritate, but also transmit diseases such as West Nile virus, malaria. and dengue.

Now, Johns Hopkins scientists have discovered what it is in the bugs’ molecular makeup that enables citronellal (the aromatic liquid used in lotions, sprays and candles) and DEET, to deter insects from landing and feeding on you. A better understanding of these molecular-behavioral links already is aiding the team’s search for more effective repellants.

In separate studies published, in Neuron and Current Biology, the Johns Hopkins researchers reveal how mosquitoes and other insects taste DEET—a man-made compound that’s been the most widely used insect repellent for more than 50 years—and smell citronellal, a commonly used botanical repellant.

Three taste receptors on the insects’ tongue and elsewhere are needed to detect DEET.  Citronellal detection is enabled by pore-like proteins known as TRP (pronounced “trip”) channels. When these molecular receptors are activated by exposure to DEET or citronellal, they send chemical messages to the insect brain, resulting in “an aversion response,” the researchers report.

“DEET has low potency and is not as long-lasting as desired, so finding the molecules in insects that detect repellents opens the door to identifying more effective repellents for combating insect-borne disease,” said Craig Montell, Ph.D., a professor of biological chemistry and member of Johns Hopkins’ Center for Sensory Biology.

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Clinical Trial Confirms Effectiveness of Water to Curb Weight Gain

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Drinking more water before meals can help promote weight loss, new research suggests. (Credit: iStockphoto/Lise Gagne)

Has the long-sought magic potion in society’s “battle with the bulge” finally arrived? An appetite-control agent that requires no prescription, has no common side effects, and costs almost nothing? Scientists report results of a new clinical trial confirming that just two 8-oz glasses of the stuff, taken before meals, enables people to shed pounds. The weight-loss elixir, they told the 240th National Meeting of the American Chemical Society (ACS), is ordinary water.

“We are presenting results of the first randomized controlled intervention trial demonstrating that increased water consumption is an effective weight loss strategy,” said Brenda Davy, Ph.D., senior author on the study. “We found in earlier studies that middle aged and older people who drank two cups of water right before eating a meal ate between 75 and 90 fewer calories during that meal. In this recent study, we found that over the course of 12 weeks, dieters who drank water before meals, three times per day, lost about 5 lbs more than dieters who did not increase their water intake.

“People should drink more water and less sugary, high-calorie drinks. It’s a simple way to facilitate weight management.”

Davy pointed out that folklore and everyday experience long have suggested that water can help promote weight loss. But there has been surprisingly little scientific information on the topic. Previous studies hinted that drinking water before meals reduces intake of calories. Lacking until now, however, has been the “gold-standard” evidence from a randomized, controlled clinical trial that compares weight loss among dieters who drink water before meals with those who do not.

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New Norwegian Earplug Solution to a Deafening Problem

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New QUIETPRO earplug with built-in noise dose meter. (Credit: Photo by Marit Hommedal/Statoil)

Some 600 cases of noise-induced hearing impairment are reported by the Norwegian petroleum industry every year. A new, intelligent earplug is now set to alleviate the problem.

Norway’s largest company, Statoil ASA, is taking the problems associated with noise exposure seriously. Over the course of four years the international energy company has led efforts to further develop an existing combined hearing protection and communication product for use on offshore platforms.

World’s most advanced hearing protection device

A microphone on the outside of the new “offshore” version of the QUIETPRO earplug picks up ambient sounds. The sound is digitally processed, and unwanted loud noises are filtered out before the sound is sent to a speaker inside the earplug. Users can adjust the level of ambient sound, as desired.

A microphone on the inside of the earplug picks up speech signals through the skull. This means that users do not have to have a microphone in front of their mouth, as is the case with the ear protection devices currently used on most offshore platforms. Another advantage is that the microphone inside the ear does not pick up background noise in the way that a microphone in front of the mouth does.

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