Fans of club music and rock concerts who like the volume cranked up to 11 but want to save their hearing might someday pop a pill rather than plugging their ears. Scientists have pinpointed the biochemical mechanism in ears that works to limit damaging effects of loud sound. When a noise registers in the brain as too loud, the protein nAChR, located on sensory hair cells in the inner ear, kicks in to limit the ability of the hair cells to respond. Mice genetically altered to produce a more potent nAChR could not hear soft sounds, and they suffered less permanent damage to their hearing when scientists blasted 100-decibel noise at their ears. "We know some drugs can modify the protein," says Paul Fuchs of Johns Hopkins University, who published the findings in the January 20 PLoS Biology. "But we need to know more about specific amounts" before a sound-protecting drug can be made. So don't toss the earplugs yet.
A Calcium Conundrum Explained
Fish excrement could solve a decades-old ocean mystery. After marine plankton die, their calcium carbonate exoskeletons dissolve, making seawater alkaline; however, past studies found that the surface waters are more alkaline than expected from plankton. Now scientists at the University of Exeter in England and their colleagues have determined that calcium carbonate "gut rocks," first found in toadfish intestines about 20 years ago, could account for a dramatic percentage of marine carbonate. Their computer models estimate roughly 812 billion to two trillion kilograms of bony fish swim in the ocean, producing some 110 billion kilograms of calcium carbonate annually. The amount constitutes at least 3 to 15 percent of the total ocean carbonate production and possibly up to 45 percent. Increasing sea temperature and rising carbon dioxide this century could cause fish to produce even more calcium carbonate, the researchers suggest in the January 16 Science.
--Charles Q. Choi
Math against Profiling
Racial profiling makes little sense, mathematically speaking. Using statistical analyses, William Press of the University of Texas at Austin has found that choosing people to screen based on ethnicity is no more effective than random checks, because nonterrorists vastly outnumber terrorists. The optimal way to screen would be to use "square-root-biased sampling," so that someone nine times as likely to be a terrorist as the average traveler would be screened three times more frequently. This approach would turn up more terrorists in part by avoiding the repeated screening of the same innocent people who fit the profile. But because that strategy would be difficult to implement, Press says that mathematically, the more sensible method is not to profile at all. The study appears in the February 10 Proceedings of the National Academy of Sciences USA.
Sonic Heat for Genes
Heating from sonic waves can turn on genes in the body, demonstrate researchers at the University Victor Segalen Bordeaux in France and their colleagues. Using mice engineered with a bioluminescent gene containing a heat-sensitive stretch of DNA, they focused high-intensity ultrasound pulses on a 0.5-millimeter-wide patch of the mice's legs, heating up that area just below the skin's surface to about 43 degrees Celsius (109 degrees Fahrenheit). Light given off revealed that the gene became active. The technique could help gene therapy, which introduces beneficial DNA into patients. When and where these genes are expressed is paramount, and currently small-molecule drugs and ionizing radiation are employed to switch genes on. But chemicals are not precise, and rays can trigger cancer. The challenge for ultrasound activation, published January 27 by the Proceedings of the National Academy of Sciences USA, is safely getting the waves deep enough to reach organs.
--Charles Q. Choi