From: David Lauter (djlauter@hotmail.com)
Date: Sat Oct 16 2004 - 08:09:23 PDT
From: "David Lauter" <djlauter@hotmail.com> Subject: hearing Date: Sat, 16 Oct 2004 08:09:23 -0700 Message-ID: <BAY13-F4zi95HfqR77b00032b57@hotmail.com>
I thought pinholers would like this clip.
David Lauter
G Washington High, SF
Ear's electrical missing link found
BY BRYN NELSON
STAFF WRITER
October 14, 2004
A tiny portion of the inner ear has apparently ensured that we're wired for
sound.
Researchers have long sought the missing link in the ear's conversion of
sound
waves into electrical signals that the brain can recognize as distinct
sounds.
In a study published yesterday in an online edition of the journal Nature,
Harvard Medical School neurobiologist David Corey and 15 collaborators found
a
prime candidate in a tiny channel located at the tips of the inner ear's
unusual
hair cells - a channel shared among humans, mice, fish and even fruit flies.
"It's something we've been looking for, for 20 years," said Corey.
The gene for the newly identified channel, known as TRPA1, adds an important
suspect to the list of three dozen genes linked to hearing loss, and the
discovery may aid the search for treatments for some of the more than 300
known
forms of inherited deafness. Corey said his group is already collaborating
with
other Harvard researchers to screen families with inherited deafness for
defects
in the TRPA1 gene.
The remarkable, almost Rube Goldberg-like progression of sound through the
human
ear leads to a snail-like structure in the inner ear known as the cochlea.
Lining the cochlea's inward spiral is a very narrow and very long ribbon of
hair
cells. Scientists have named these hair cells for their tufts of up to 300
microscopic cilia that sway back and forth in response to vibrations, almost
like sea anemones waving in the ocean. Tiny strings linking the hairs
together
loosen and tense in response to the movement, Corey said, effectively
opening
and closing small channels.
When open, the channels allow ions like potassium to rush in and create an
electrical voltage, creating a signal that zips from connected neurons to
the
brain, which then perceives the signal as sound.
But researchers couldn't pinpoint the agent of the transformation from sound
vibrations to nerve impulses until the completed DNA sequences of fruit
flies,
mice and humans revealed candidates in a family of related ion channels. In
mice
and frogs, molecular probes revealed that one candidate protein localized to
the
tips of the hair cell's cilia, where scientists knew the mystery channel
ought
to be. And when the researchers blocked production of that protein, TRPA1,
hair
cells in both zebrafish and mice no longer responded to mechanical
vibrations.
Dr. John S. Oghalai, an assistant professor of otolaryngology at Baylor
College
of Medicine in Houston who wasn't involved in the study, hailed it as "a
major
discovery."
Although researchers suspected that the inner ear's hair cells contained
such a
channel, Oghalai said its identification could mark the beginning of a new
search for inherited deafness treatments. Since the channel acts as a sensor
that converts vibrations to electrical signals, Oghalai said it also could
prove
"revolutionary" for mechanical engineering applications that require a
similar
conversion process.
Copyright © 2004, Newsday, Inc.
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