Audiology In Brief Earwax comes in two types, wet and dry. The wet form is found in 97% of the population in Africa and Europe, the dry form predominates among East Asians, and each type is found in approximately half the population of southern and central Asia. By comparing the DNA of ... News in Brief
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News in Brief  |   June 01, 2010
Audiology In Brief
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Hearing Disorders / News in Brief
News in Brief   |   June 01, 2010
Audiology In Brief
The ASHA Leader, June 2010, Vol. 15, 5. doi:10.1044/leader.NIB.15072010.5
The ASHA Leader, June 2010, Vol. 15, 5. doi:10.1044/leader.NIB.15072010.5
Earwax Gene
Earwax comes in two types, wet and dry. The wet form is found in 97% of the population in Africa and Europe, the dry form predominates among East Asians, and each type is found in approximately half the population of southern and central Asia. By comparing the DNA of Japanese people with each type of earwax, researchers were able to identify the gene that controls earwax type, according to the March 2006 issue of Nature Genetics.
The researchers found that the switch of a single DNA unit in the gene determines whether a person has wet or dry earwax. This DNA change deactivates the gene, and without its contribution a person has dry earwax. The earwax-affecting gene, known as the ATP-binding cassette C11 gene, lies with three other genes in a long stretch of DNA that has little variation among individuals. The single mutation in the earwax gene is one in which a G (for guanine) is replaced with an A (for adenine). People who inherit the version of the gene that has A from both parents have dry earwax. Individuals who carry two of the G versions, or one G and one A, have wet earwax. Visit Nature Genetics for an abstract.
Protection Against NIHL
A stress-response system within the cochlea mirrors the signaling pathways of the body’s fight-or-flight response, according to researchers at Tufts University medical school.
The current theory of protection against noise-induced hearing loss (NIHL) states that signals from the cochlea travel to the brain and back, a system that requires moderately high-intensity sounds to function. This study demonstrates that a previously unrecognized signaling system involved in NIHL exists entirely within the ear and operates at lower-intensity sounds typically found in the everyday environment.
“The local signaling system that we identified in the cochlea mirrors the molecular signaling pathways of the body’s physiological fight-or-flight response, which is triggered by the release of molecules from the adrenal glands during times of physical stress,” said Doug Vetter, senior author and lecturer in the Department of Neuroscience at Tufts University School of Medicine.
“It may be that activation of the cochlea’s protective mechanism from physical stress changes the way the cells of the inner ear respond to the next exposure,” he said. “In this way, protection may be established based on previous exposures and prior to the next exposure to potentially damaging sounds.” For an abstract, view the May issue of Neurobiology of Disease online.
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June 2010
Volume 15, Issue 7