NIH-funded science on hearing loss in pre-term infants, people with autoimmune disease to be featured at international research meeting in Baltimore
What: NIH-supported scientists will be presenting their latest research findings at the 2011 Midwinter Meeting of the Association for Research in Otolaryngology (ARO).
When: February 19-23, 2011
Where: Baltimore Marriott Waterfront Hotel, Baltimore, Md.
Additional Information: Research topics to be presented by scientists supported by the National Institute on Deafness and Other Communication Disorders (NIDCD) will include:
Deafness and the double helix: What our DNA is teaching us about hearing and hearing loss
Nearly 70 genes have been identified that cause hereditary hearing loss so far, and many more gene candidates continue to be investigated. In this Presidential Symposium lecture, NIDCD director James F. Battey, Jr., M.D., Ph.D., provides a real-time snapshot of where we stand in the study of genes and hearing loss. He'll share how advances in genome science have greatly enhanced our understanding of the molecular mechanisms that govern how we hear and will discuss how two new resources—the Knockout Mouse Phenotyping Program (KOMP2) and Genome-Wide Association Studies (GWAS)—show special promise in the coming years. KOMP2, an international effort to study the characteristics of mice after a gene has been inactivated, will generate hundreds of new mouse models for studying hearing loss. GWAS, a system for rapidly scanning people's genomes for variants that might be associated with a disease, will provide an opportunity to pinpoint the genes responsible for other, more genetically complex communication disorders, such as autism, specific language impairment, and age-related hearing loss, or presbycusis.
The talk "Genes and Deafness" will take place Saturday, Feb. 19, at 8:40 a.m. in Harborside Ballroom A-C.
In autoimmune-related hearing loss, inflammation may not be the culprit
New way of thinking may help us find more effective treatment with fewer side effects
People who have an autoimmune disease—such as lupus or rheumatoid arthritis—also frequently experience hearing loss, and the conventional wisdom is that this is due to inflammation in the inner ear. As a result, most doctors will typically prescribe glucocorticoids, a family of steroids that quell the inflammation and improve hearing, but can have serious side effects if taken too long. NIDCD-funded researchers from Oregon Health & Science University see things a different way. Their research shows that, although glucocorticoids may help improve hearing, they don't seem to be acting on inflammation, which isn't present in autoimmune mouse models with hearing loss. Rather, they seem to be correcting an imbalance in ions in the fluid of the inner ear, which is the more likely source of hearing loss. In this study, the researchers looked at gene expression in autoimmune mice with hearing loss and found that 22 of the 24 genes regulating ion concentration in the inner ear were turned off. Genes that regulate the inflammatory response also were not activated, which is the opposite of what you'd expect to find if inflammation were involved. When the mice received glucocorticoid treatment, the expression of several ion-regulating genes significantly increased, while there was no effect on inflammation. What's happening, the researchers suggest, is that glucocorticoid molecules are attaching themselves to receptors for another steroid group, called mineralocorticoids, whose job is to maintain proper ion balances in the inner ear. The researchers propose that developing a treatment that is based on regulating ion concentration instead of controlling inflammation may be more effective and offer fewer side effects for people with autoimmune diseases as well as some other hearing and balance disorders, such as sudden hearing loss and Ménière's disease.
The poster "Cochlear Ion Homeostasis Mechanisms Are Suppressed in Autoimmune Inner Ear Disease and Restored by Glucocorticoid Treatment" will take place Sunday, Feb. 20, at 1:00 p.m. in the Grand Ballroom.
Learning to bear unbearable sounds
Almost all of us cringe at the thought of fingernails on a chalkboard, but people with hyperacusis experience discomfort when listening to normal sounds too. For them, some sounds seem too loud, even though they are at tolerable levels for everyone else. Some people may even go without their hearing aids to avoid the pain or discomfort that amplified sound can bring. NIDCD-funded researchers at the University of Alabama, University of Maryland, and others tested how a sound therapy for tinnitus (ringing in the ears) can help people with hyperacusis to tolerate louder sounds. In earlier studies, they'd found that people with tinnitus who received sound therapy—wearing a noise-generating device in each ear that plays a soft whooshing noise, like the inside of a seashell, plus counseling—were able to tolerate louder sound levels than they did before the treatment. In a randomized, double-blind, placebo-controlled clinical trial, the researchers tested various combinations of sound therapy with hearing-impaired individuals who had low sound tolerance, but who didn't have ringing in the ears as their primary problem. Some received counseling and the noise generators, some received counseling with placebo noise generators, some received noise generators with no counseling, and some received placebo noise generators with no counseling. They found that individuals were much more likely to increase their tolerance for louder sound levels when using the full treatment—noise generators plus counseling. The researchers' next step is to evaluate a noise-generating device in combination with a hearing aid to see if they can enhance performance for hearing aid wearers by improving their tolerance to amplified sounds.
The poster "Intervention for Restricted Dynamic Range and Reduced Sound Tolerance: Clinical Trial Using Modified Tinnitus Retraining Therapy" will take place Saturday, Feb. 19, at 1:00 p.m. in the Grand Ballroom.
Pre-term infants are at higher risk for rare form of hearing loss
Selective loss of key sensory cells is possible sign of auditory neuropathy
It's well known that infants born prematurely have a higher risk for hearing loss, but what's been unclear to this point is the reason why. NIDCD-funded researchers from the Massachusetts Eye and Ear Infirmary, Harvard University, and Universidade de Sao Paolo, Brazil, set out to find the answer by conducting a postmortem examination of the temporal bones—the part of the skull that houses the inner ear—of 50 infants from the neonatal intensive care unit (NICU) of a hospital in San Jose, Costa Rica. They found that in four out of 27 pre-term babies—eight ears in all—the sensory cells that help amplify sound vibrations, called outer hair cells, appeared healthy, while the sensory cells that convert those vibrations to electrical signals that travel to the brain, the inner hair cells, were preferentially destroyed. Conversely, in the 23 full-term NICU babies, only one ear out of 46 ears showed this selective inner hair cell loss. The findings are surprising, since outer hair cells are very delicate and most hearing loss in people is due to dysfunction, damage, and death of these sensory cells, in comparison to inner hair cells, which are much more resistant to damage. When inner hair cells are destroyed, the hearing signal never reaches the brain, even if the outer hair cells are still functioning normally. This condition is known as auditory neuropathy. The findings help explain why other researchers have observed a higher incidence of auditory neuropathy in pre-term babies and suggest that the underlying pathology in auditory neuropathy is not actually due to loss of neurons, as the name implies, but to loss of the inner ear sensory cells that drive them.
The poster "Selective Inner Hair Cell Loss in Premature Infants" will take place Sunday, Feb. 20, at 1:00 p.m. in the Grand Ballroom.
Two drugs may be better than one in treating, preventing noise-induced hearing loss
Combination therapy—the use of two or more drugs in combination to treat an illness—is an effective way to treat such complex diseases as HIV/AIDS and cancer. Now some researchers are wondering if it might be effective in treating noise-induced hearing loss (NIHL) too. The causes of NIHL involve a number of complex cellular and molecular pathways. Some of these pathways are already targeted by FDA-approved drugs for the treatment of other diseases. Researchers from the Washington University in St. Louis wondered, 1) if FDA-approved drugs that target these shared signaling pathways might be effective in preventing or treating NIHL, and 2) if so, is it possible to reduce their dosages—therefore to reduce their side effects—by combining two drugs that act on different signaling pathways? Previous studies have shown that synthetic steroids, called corticoids, can prevent NIHL, and this team had recently found that anticonvulsants (for the treatment of epilepsy) can prevent permanent NIHL in mice. In this study, they investigated four drugs against NIHL, two drugs from the anticonvulsant family and two from the family of synthetic steroids. The researchers gave various doses of each drug to mice either two hours before exposing them to loud noise or 24 hours after exposure. After the range of effective dosages was determined for each drug, they applied a mathematical simulation to combine two drug families, and found that certain combinations were indeed effective in protecting against permanent hearing loss at lower dosages. They are currently applying for a patent on this discovery. The researchers' next step is to examine the effects of the drug combination on animals that have a hearing range that is more similar to humans. They also plan to test the drug pairs on extremely loud noise, similar to what troops are facing on an Afghanistan battlefield.
The poster "Development of a Combination Therapy for Noise-induced Hearing Loss" will take place Monday, Feb. 21, at 1:00 p.m. in the Grand Ballroom.
Kermit's conundrum: How to tell who's who in a chorus of croakers
If you think it's difficult trying to hear what someone is saying at a cocktail or dinner party, imagine how a tree frog feels. Looking for a potential mate, they're trying to key in on a specific song in a swamp filled with a half dozen or so other frog species, each singing a slightly different tune. How do they do it? Researchers from the University of Minnesota wanted to find out how much pitch plays a part. They simulated the call of the gray tree frog, a high-pitched series of pulses that last about a second, and embedded that call with a call simulating that of the American toad, a sequence of high-pitched tones that pulses at about the same rate but lasts a lot longer. While the female tree frog is listening for a call of 50 pulses per second, the interwoven recordings produced a call that was twice as fast, or 100 pulses per second, which she ignored. The researchers then varied the pitch, or frequency, between the frog's song and the toad's song and measured how long it took for the female to respond. If the calls were too close in frequency, the females fused them, but as the frequencies became separated, they were able to discern the tree frog song and moved toward it. The farther apart in pitch they were, the faster the females responded. These findings are quite similar to how humans discern overlapping voices at a party, even though several key features of the two auditory systems—tree frogs and humans—likely evolved independently of one another. The researchers suggest that by learning how distantly related vertebrates have solved similar communication problems, we can better understand the ways that auditory systems process information encountered in a noisy environment.
The poster "Source Segregation Based on Frequency Differences Facilitates Vocal Communication in Frog Choruses" will take place Tuesday, Feb. 22, at 1:00 p.m. in the Grand Ballroom.
For more information about the Association for Research in Otolaryngology, visit their website at www.aro.org.
NIDCD supports and conducts research and research training on the normal and disordered processes of hearing, balance, smell, taste, voice, speech and language and provides health information, based upon scientific discovery, to the public. For more information about NIDCD programs, see the Web site at www.nidcd.nih.gov.
The National Institutes of Health (NIH)—The Nation's Medical Research Agency—includes 27 Institutes and Centers and is a component of the U. S. Department of Health and Human Services. It is the primary federal agency for conducting and supporting basic, clinical, and translational medical research, and it investigates the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.
