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Topic: Stereocilia

In the News (Tue 29 Dec 09)

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	ASA/NOISE-CON 2000 Lay Language Papers -Nanoscale Ears based on Artificial Stereocilia
		Stereocilia are rod-like structures (Figure 1) found in the cochlea (inner ear) of all hearing animals.
		Fluid in the statocyst moves the stereocilia relative to the organ's statolith, compacted sand grains that are assimilated by the lobster.
		Relative to membrane-based acoustic sensors, stereocilia effectively increase the capture of flow energy through a mechanical lever advantage while preserving the size of the projected area (attachment surface), a property that can be exploited to enable a high degree of miniaturization without loss of sensitivity.
	www.acoustics.org /press/140th/noca.htm (1703 words)

	How the Ear Works: Steoeocilia Bundle Organization and Mechanotransduction
		The bending of the bundle is a mechanical event which is why hair cells are mechanoreceptors (photoreceptors and chemoreceptors change their membrane potential in response to light and chemicals respectively, the change in the membrane potential of a sensory receptor cell in response to an appropriate stimulus is called a receptor potential).
		This arrangement is asymmetrical and polarized because the stereocilia are arranged in rows of short, intermediate and tall stereocilia.
		Each hair cell therefore codes the direction and degree of stereocilia bundle bending by either increasing or decreasing the firing rate of the postsynaptic afferent fiber in proportion to the magnitude of the bend.
	www.bcm.edu /oto/research/cochlea/Volta/10.html (0 words)

	Researchers Discover Mechanism Underlying Stereocilia Self-Renewal
		Stereocilia are arranged in varying lengths, similar to a stack of soda straws graded in height forming a staircase-like bundle, to accommodate the different energies found in different frequencies of sound waves.
		The stereocilia, which are largely made up of the building block protein, actin, rebuilds itself continuously, maintaining the overall structure.
		Mutations in the gene for myosin are known to prevent stereocilia elongation.
	www.nidcd.nih.gov /news/stories/04/04_19_04.asp (409 words)

	Stereocilia (Site not responding. Last check: )
		Stereocilia are mechanosensing organelles of hair cells, which respond to fluid motion or fluid pressure changes in numerous types of animals for various functions, primarily hearing.
		When the stapes causes sound waves in the endolymphatic fluid in the cochlea, the stereocilia are deflected by shear force, which results in the mentioned electrical signal for the hair cell.
		Stereocilia (along with the entirety of the hair cell) in mammals can be damaged or destroyed by excessive loud noises, disease, and toxins and are not regeneratable (6).
	www.guideofpills.com /Stereocilia.html (903 words)

	Stereocilia Dr.Jastrows EM-Atlas
		Stereocilia of inner and outer hair cells of the organ of Corti in the inner ear are about 5 µm in length.
		Sensory stereocilia are similar in construction and appearance to microvilli with the following exceptions: they are longer and greater in diameter, their basis is thinner than the parts located above; a glycocalyx and antennulae are not encountered.
		Stereocilia belong to secondary sensory cells and change the frequency of generated action potentials depending on direction when being sheared or bend.
	www.uni-mainz.de /FB/Medizin/Anatomie/workshop/EM/EMStereociliaE.html (387 words)

	Rat Genome Database: References
		Stereocilia contain a central core of actin filaments, cross-linked by actin bundling proteins.
		During postnatal development of the rat organ of Corti, T-plastin can be detected in the core of stereocilia from early stages of hair cell differentiation, and its expression gradually increases in stereocilia as hair cells mature.
		However, as opposed to other actin-binding proteins expressed in stereocilia, T-plastin is absent from the stereocilia of mature hair cells.
	rgd.mcw.edu /generalSearch/RgdSearch.jsp?quickSearch=1&searchKeyword=RGD:731234 (269 words)

	[No title] (Site not responding. Last check: )
		The stereocilia are oriented in rows of ascending height, with the tallest lying next to the lone kinocilium.
		Deflection of the stereocilia toward the kino cilium causes potassium channels in the apical portions of the stereocilia and kinocilium to open.
		Given that deflections of the stereocilia toward and away from the kinocilium cause opposing physiologic responses, it is clear that the directional orientation of the hair cells in the vestibular organs will play an essential role in sig naling the direction of movement.
	vestibular.wustl.edu /vestibular2.html (1216 words)

	ScienceDaily: NIDCD Scientists Report New Findings On Inner Ear Hair Cell Stereocilia Formation
		Stereocilia are essential components for the normal hearing process since they convert mechanical energy of sound pressure into electrical signals, which sensory hair cells then direct to the brain.
		Mutations of two known genes, myosin-XVa and whirlin, underlie stereocilia pathology in shaker 2 and whirler mice.
		Belyantseva and co-authors report that hair cells from shaker 2 mice with short stereocilia were maintained in culture and after injection with a compact form of the gene (cDNA) for myosin-XVa, the normal hair cell stereocilia staircase architecture was restored.
	www.sciencedaily.com /releases/2005/02/050210234728.htm (832 words)

	H.E.A.R. \| Articles \| Hearing Education and Awareness for Rockers (Site not responding. Last check: )
		The bottom of these cells are attached to the basilar membrane, and the stereocilia are in contact with the tectoral membrane.
		They are shaped cylindrically, like a can, and have stereocilia at the top of the cell, and a nucleus at the bottom.
		When the stereocilia are bent in response to a sound wave, an electromotile response occurs.
	www.hearnet.com /features/articles/artist_article_hearhair.shtml (729 words)

	The Scientist : Hear today, gone the day after tomorrow
		Stereocilia — also known as hair bundles — are mechanosensitive organelles in the inner ear that translate sounds into nervous signals by detecting displacements in the air, but the mechanisms involved in their maintenance have been unclear.
		In August 22 Nature, Mark Schneider and colleagues at the National Institutes of Health, Bethesda, US, show that that the auditory hair bundles are continuously remodeled by the addition of actin monomers to stereocilium tips and that the entire core of the stereocilium is renewed 50 times faster than was previously thought (Nature 2002, 418:837-838).
		"This unexpected dynamic feature of stereocilia will help our understanding of how auditory sensory function develops and is maintained.[...] Our discovery that the renewal of stereocilia is dynamic may be of value in the investigation of conditions associated with malformation or disruption of stereocilia," conclude the authors.
	www.the-scientist.com /article/display/20620 (231 words)

	Chapter 4b - Sensory Receptors II
		The stereocilia are connected together by a filamentous process, the tip link, which passes obliquely between the distal end of one stereocilium and the side of the longest adjacent one.
		According to this model, a stimulus that displaces the stereocilia toward the kinocilium (or in the direction where the kinocilium would be in the auditory system), elongates the tip link that pulls on the mechanical gate and opens it.
		Conversely, when the stereocilia are displaced away from the kinocilium, the tension on the tip link is reduced (perhaps it shortens) reducing the pull on the mechanical gate and closing it.
	www.unmc.edu /Physiology/Mann/mann4b.html (3118 words)

	Chap V
		Movement of the auxiliary structure relative to the hairs displaces the cilia, and this displacement is the adequate stimulus for activating the hair cell.
		A single kinocilium is present, which differs in structure from stereocilia and which is asymmetrically placed at one edge of the stereocilial bundle, usually adjacent to the tallest of these (in the cochlea the kinocilium is present in early development but is absent in the adult).
		Thus, interfering with ion-channel operations or changing the physical arrangement of the stereocilia is sufficient to alter mechanoelectrical transduction in the inner ear.
	www.neurophys.wisc.edu /h&b/textbook/chap-5.html (1387 words)

	Rapid turnover of stereocilia membrane proteins: evidence from the trafficking and mobility of plasma membrane Ca(2+)-AT
		Rapid turnover of stereocilia membrane proteins: evidence from the trafficking and mobility of plasma membrane Ca(2+)-ATPase 2.
		Using immunofluorescence, we determined that PMCA2 is enriched in the stereocilia and present at a relatively low concentration in the kinocilium and in the remaining apical membrane.
		Using an antibody to the extracellular domain of PMCA2 as a probe, we observed that PMCA2 diffuses laterally from the stereocilia membrane and is internalized at the apical cell border maintaining an estimated half-life of residency in the stereocilia of approximately 5-7 h.
	www.galenicom.com /medline/article/16763047/mt:Mechanoreceptors (422 words)

	Myosin-VI
		The cuticular plate is found at the base of the stereocilia, the actin-based protrusions that serve to sense and transmit mechanoelectrical impulses.
		The stereocilia are polarized, with their pointed ends embedded in the cuticular plate, so myosin-VI may also be required to transport components down the stereocilia.
		Snell's waltzer mice have defects in the assembly of stereocilia and it has been suggested that myosin-VI may be pulling the membranes down between each stereocilium during hair cell development (Self et al 1999).
	www.proweb.org /myosin/Myo6.html (452 words)

	An actin molecular treadmill and myosins maintain stereocilia functional architecture and self-renewal -- Rzadzinska et ...
		Stereocilia maintained their lengths as evident in the bottom left panel where actin-GFP fluorescence had reached the base of the stereocilia, yet the stereocilia length is similar to the neighboring nontransfected cell.
		Stereocilia tips of the tallest row of the bundle are prolate in shape with an electron-dense region just below the stereocilia membrane (A, arrows), where intense myosin XVa labeling is visualized by immunofluorescence or by immunogold EM (A, arrowheads).
		The second row stereocilia in the bundle are prolate and pointed (B) with a smaller discrete electron-dense region at the end of their longest actin filaments (B, arrow), which also coincides to where myosin XVa is visualized by either fluorescence or by immunogold EM (B, arrowheads).
	www.jcb.org /cgi/content/full/164/6/887 (7730 words)

	Sondag_chapter2
		It is hypothesized that the initial stages and duration of otoconia genesis are demar-cated by organic fibrils (muco-polysaccharides and mucoproteins) attached to the stereocilia.
		The kinocilium is connected to specific stereocilia and the stereocilia are interconnected with each other through strands of macromolecules (tip links) running from the top of one stereocilium into the side of the tallest neighbour (Ross et al, 1987; Takumi-da et al, 1992).
		These fibrils are absent in the stereocilia that are packed with actin filaments, which are added to the stereo-cilia during growth (Shepherd 1994).
	www.desc.med.vu.nl /Publications/Thesis/Sondag/Sondag_chapter2.htm (2815 words)

	David P. Corey
		Stereocilia are connected at their tips by fine filaments called tip links, which are pulled each time the bundle is deflected in one direction by a sound vibration.
		Tip links are thought to pull directly on ion channels in the tips of the stereocilia, which open in response to the tension, allowing electric current in the form of potassium ions to flow into the hair cell to change its internal voltage.
		Antibodies labeled the tips of the stereocilia in both frog and mouse hair cells, where we expect transduction channels to be located.
	www.hhmi.org /research/investigators/coreydp.html (1269 words)

	HHMI Bulletin September 2005: The Importance of Being Cilia
		Stereocilia are not true cilia—they are instead microvillae, based on the structural protein actin, with no tubulin (the protein that makes up microtubules) present.
		Stereocilia vary in height, becoming progressively shorter the farther they are from the long kinocilium at the edge of the bundle.
		Signal transduction in hair cells involves movement of the stereocilia in the direction of the kinocilium—or rather, where the kinocilium was.
	www.hhmi.org /bulletin/sept2005/features/cilia6.html (726 words)

	Sound from Silence - How Hair Cells Work
		Hudspeth and his colleagues used the electrodes to record the electric activity within the hair cells as he gently pushed against their stereocilia with a small, precisely controlled probe.
		Hair cells, like all excitable nerve cells, are tiny batteries, with an excess of negatively charged ions inside and an excess of positively charged ions outside.
		Through a series of biochemical steps, this depolarization causes the hair cell to release neurotransmitter molecules--chemicals that transmit the electric signal from one nerve to another--that drift across a small space to receptors on nerve cells.
	www.beyonddiscovery.org /content/view.asp?I=259 (402 words)

	Hair clue to temporary deafness - 22 August 2002 - New Scientist
		They discovered that the stereocilia were being continually regenerated from tip to base, and were totally replaced within two days.
		"Stereocilia bend in response to sound waves and it is thought that excessive exposures from rock concerts or gunshots cause the stereocilia to make extreme bending movements, says lead researcher Bechara Kachar from the National Institute on Deafness and other Communication Disorders, National Institutes of Health in Bethesda, Maryland
		And our results suggest that the damaged portion of the stereocilia could be replaced as the entire stereocilia actin backbone is renewed.
	www.newscientist.com /news/emailafriend.jsp?id=ns99992707 (458 words)

	Stereocilia - Karr.net (Site not responding. Last check: )
		Stereocilia are apical modifications of the cell, which are distinct from microvilli and cilia.
		Though their name is more similar to cilia, they are actually more closely related to microvilli, and some sources consider them to be a variant of microvilli rather than their own distinct type of structure.
		Find stereocilia info at Netster.com - Netster.com makes it fast and easy to find stereocilia information.
	209.197.127.220 /encyclopedia/Stereocilia (279 words)

	inner ear hearing impairment deafness cochlea tinnitus sound auditory gummer
		As with mechanoelectrical transduction in the stereocilia, the process must be exceedingly fast because it is required to work up to ultrasonic frequencies.
		The hypothesis that the relevant high-frequency electromechanical transducer is located in the stereocilia has the advantage that it does not suffer from low-pass filtering by the stereocilia membrane.
		However, emissions do not allow a differential diagnosis of the cochlear amplifier – for example, to decide whether malfunction is due to decoupling of the stereocilia of the outer hair cells from the overlying tectorial membrane, or due to disruption of the motor complex in the basolateral wall of the outer hair cell, or ….
	www.uni-tuebingen.de /cochlea/research.htm (1656 words)

	Changes of Hair Cell Stereocilia and Threshold Shift after Acoustic Trauma in Guinea Pigs: Comparison between Inner and ...
		Stereocilia changes and threshold shifts of auditory brainstem responses (ABR) were assessed at regular intervals after noise exposure for 9 weeks.
		The shift of ABR threshold was not parallel to the chronological change of the stereocilia on IHCs as well as OHCs.
		The elevation of the ABR threshold (40-60 dB SPL) was greatest on the 1st day after noise exposure, whereas the stereocilia showed the most damage 7 days after noise exposure.
	content.karger.com /ProdukteDB/produkte.asp?Doi=75224 (255 words)

	18th International Mouse Genome Conference (2004)
		Stereocilia on the surface of hair cells are vital for the process of auditory transduction.
		Stereocilia develop in bundles with a regular staircase pattern, whose actin core is organised such that the barbed ends of actin filaments are located at the stereocilia tips where there is a continuous cycle of renewal of actin filaments by addition of actin monomers.
		Expression of whirlin is dynamic during stereocilia growth demonstrating an ordered appearance and fade-out across the stereocilia rows and revealing a novel molecular gradation of process traversing the developing stereocilia bundle.
	www.imgs.org /abstracts/2004abstracts/abs/file54.shtml (324 words)

	Radixin deficiency causes deafness associated with progressive degeneration of cochlear stereocilia -- Kitajiri et al. ...
		Stereocilia are intensely stained with anti-radixin mAb, and weakly but reproducibly stained with anti-ezrin mAb (arrows).
		In addition to stereocilia arrays carrying central tubulin-based kinocilium (arrows in c and d), hair cells as well as supporting cells are covered with large numbers of short conventional microvilli that have mostly disappeared in adult mice.
		radixin-based stereocilia (a), and during the process of degeneration, these stereocilia as well as core bundles appeared to be fused to form abnormal thick and short protrusions (c and d).
	www.jcb.org /cgi/content/full/166/4/559 (7228 words)

	Hear, hear: key ear part regenerates - Biology - Brief Article Science News - Find Articles
		Scientists have now discovered that stereocilia are in a state of continuous regeneration.
		To probe how stereocilia arise, Kachar and his colleagues kept the excised ears of newborn mice alive in laboratory dishes.
		The stereocilia eventually incorporated the protein throughout their whole length.
	www.looksmarthiking.com /p/articles/mi_m1200/is_10_162/ai_91971051 (316 words)

	AHG: tip links_e
		If, however, the transduction channels were located at the end of the hair bundle's tip links, not more than 1/250 of the stimulus energy could be used to change the open probability of the channels [Gitter, 1994, HNO 42: 327-333].
		Therefore, I propose that the transduction channels of hair cells are connected to the short row-to-row horizontal links at the distal ends of neighboring stereocilia.
		The force in the gating springs that is counteracting the movement of the transduction channels may be varied in the process of adaptation by an active motor, as has been proposed in other investigations.
	www.medizin.fu-berlin.de /klinphys/themen_ahg/ear3_tiplinks_e.htm (321 words)

	Defects in whirlin, a PDZ domain molecule involved in stereocilia elongation, cause deafness in the whirler mouse and ...
		In contrast, mutant OHC stereocilia are closer to normal in length but are arranged in a rounded 'U' shape instead of the normal 'V' or 'W' shape, and stereocilia at the edges of rows are shortened.
		We detected whirlin from E18.5 onwards in the five vestibular compartments (saccule, utricle and the three cristae ampullares of the semicircular canals) and the cochlea, where it was restricted to the hair cells (Fig.
		Stereocilia of the IHC were more strongly labeled by whirlin-Nt than those of the OHC, which were only faintly stained (Fig.
	www.nature.com /cgi-taf/DynaPage.taf?file=/ng/journal/v34/n4/full/ng1208.html (6337 words)

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