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The study won't tell you, but yep, it's melanin, again. Can you hear me now?
U.S. Hearing Loss On The Rise
A recent study found that one in three U.S. adults already show signs of early hearing loss.
Researchers at Johns Hopkins University in Baltimore noted that the increase in use of personal stereos and an aging population may amount to a hearing impairment epidemic.
They estimated that 55 million Americans have hearing loss in one or both ears, with men, whites and the least-educated most affected.
In the Archives of Internal Medicine, researchers noted that 29 million, or one out of six, adults have some trouble discerning speech.
"The prevalence of hearing loss in the United States is predicted to rise significantly because of an aging population and the growing use of personal listening devices. Indeed, there is concern that we may be facing an epidemic of hearing impairment," Dr. Yuri Agrawal of the Baltimore hospital wrote.
It is common for people to ignore or disavow hearing loss, the researchers said, leading to difficulty communicating that can result in productivity problems at work, depression, and less access to health care that ultimately raises the risk of sickness and death.
Hearing loss is common among people 70 and older, according to the report. But hearing loss also affected 8.5 percent of those in their 20s and 17 percent of people in their 30s.
Researchers noted that exposure to workplace noise, firearms, and loud music were all risk factors.
They studied health information from 5,700 Americans between the ages of 20 and 69 years between 1999 and 2004 in the federal National Health and Nutrition Examination Survey. Agrawal and colleagues found men were twice as likely as women (21 percent versus 11 percent) to have speech-frequency hearing loss in one or both ears.
Whites were more than twice as prone to hearing loss than blacks, and those with less education were more at risk than those who completed high school or beyond.
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Hearing loss is common among people 70 and older, according to the report.But hearing loss also affected 8.5 percent of those in their 20s and 17 percent of people in their 30s.
Researchers noted that exposure to workplace noise, firearms, and loud music were all risk factors.
Of course Heavy Metal and Hard Rock, those soothing types of sounds, are no doubt the culprits. And not to be left out the Michigan militia groups get their hearing problems from a variety of weapons all going off at the same time.
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Ching-Shen Lin, MD; Frederick G. Zak, MD Arch Otolaryngol. 1982;108(8):489-490.
Abstract
• Melanocytes are present in the lamina propria of the middle ear mucosa of young children to elderly adults in both whites and blacks. Melanin pigment also is seen in the epithelial cells, so-called melanogenic metaplasia. The melanocytes in the middle ear mucosa are of neural crest origin and their presence explains melanocytic tumors at this anatomic site.
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Generation of human melanocytes from induced pluripotent stem cells
PLoS One. 2011 Jan 13;6(1):e16182.
Ohta S, Imaizumi Y, Okada Y, Akamatsu W, Kuwahara R, Ohyama M, Amagai M, Matsuzaki Y, Yamanaka S, Okano H, Kawakami Y. Division of Cellular Signaling, Institute for Advanced Medical Research, Keio University School of Medicine, Tokyo, Japan.
Abstract
Epidermal melanocytes play an important role in protecting the skin from UV rays, and their functional impairment results in pigment disorders. Additionally, melanomas are considered to arise from mutations that accumulate in melanocyte stem cells. The mechanisms underlying melanocyte differentiation and the defining characteristics of melanocyte stem cells in humans are, however, largely unknown. In the present study, we set out to generate melanocytes from human iPS cells in vitro, leading to a preliminary investigation of the mechanisms of human melanocyte differentiation. We generated iPS cell lines from human dermal fibroblasts using the Yamanaka factors (SOX2, OCT3/4, and KLF4, with or without c-MYC). These iPS cell lines were subsequently used to form embryoid bodies (EBs) and then differentiated into melanocytes via culture supplementation with Wnt3a, SCF, and ET-3. Seven weeks after inducing differentiation, pigmented cells expressing melanocyte markers such as MITF, tyrosinase, SILV, and TYRP1, were detected. Melanosomes were identified in these pigmented cells by electron microscopy, and global gene expression profiling of the pigmented cells showed a high similarity to that of human primary foreskin-derived melanocytes, suggesting the successful generation of melanocytes from iPS cells. This in vitro differentiation system should prove useful for understanding human melanocyte biology and revealing the mechanism of various pigment cell disorders, including melanoma.
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