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Assessing morphology and function of the semicircular duct system: introducing new in-situ visualization and software toolbox

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ABSTRACT

The semicircular duct system is part of the sensory organ of balance and essential for navigation and spatial awareness in vertebrates. Its function in detecting head rotations has been modelled with increasing sophistication, but the biomechanics of actual semicircular duct systems has rarely been analyzed, foremost because the fragile membranous structures in the inner ear are hard to visualize undistorted and in full. Here we present a new, easy-to-apply and non-invasive method for three-dimensional in-situ visualization and quantification of the semicircular duct system, using X-ray micro tomography and tissue staining with phosphotungstic acid. Moreover, we introduce Ariadne, a software toolbox which provides comprehensive and improved morphological and functional analysis of any visualized duct system. We demonstrate the potential of these methods by presenting results for the duct system of humans, the squirrel monkey and the rhesus macaque, making comparisons with past results from neurophysiological, oculometric and biomechanical studies. Ariadne is freely available at http://www.earbank.org.

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Raw visualizations of stained membranous labyrinths through micro-CT scanning.(a–g) Soft-tissues structures contained inside the bony labyrinth of the human (c,d), rhesus macaque (b,e,g) and squirrel monkey (a,f) specimens. Aa, Ap, Al, anterior, posterior and lateral ampullae, respectively; Ca, Cl, anterior and lateral cupulae (artificially shrunk); CC, common crus; CD, cochlear duct; Cra, Crp, Crl, anterior, posterior and lateral cristae ampullares; S, sacculus; Sa, Sp, Sl, slender parts of the anterior, posterior and lateral semicircular ducts; Sm, macula sacculi; ST, scala tympani; SV, scala vestibuli; Ua, anterior utriculus; Um, macula utriculi. Scale bar is 0.5 mm.
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f1: Raw visualizations of stained membranous labyrinths through micro-CT scanning.(a–g) Soft-tissues structures contained inside the bony labyrinth of the human (c,d), rhesus macaque (b,e,g) and squirrel monkey (a,f) specimens. Aa, Ap, Al, anterior, posterior and lateral ampullae, respectively; Ca, Cl, anterior and lateral cupulae (artificially shrunk); CC, common crus; CD, cochlear duct; Cra, Crp, Crl, anterior, posterior and lateral cristae ampullares; S, sacculus; Sa, Sp, Sl, slender parts of the anterior, posterior and lateral semicircular ducts; Sm, macula sacculi; ST, scala tympani; SV, scala vestibuli; Ua, anterior utriculus; Um, macula utriculi. Scale bar is 0.5 mm.

Mentions: We found that all parts of the semicircular duct system, including the ducts, utricle, ampullae, and cupulae, can be successfully visualized with micro-CT after staining with phosphotungstic acid (PTA)33 (Fig. 1) Tissue fixation should happen within a few days after death, preferably using Bouin solution, and a specimen should not have been frozen as this invariably destroys the delicate membranous labyrinth. Visualization with micro-CT requires a voxel size of less than 20 μm, and a scanning protocol which provides the best available image quality, low noise levels in particular. The most productive approach for 3D visualization and digital quantification of the membranous labyrinth, including the semicircular duct system, is by surface rendering rather than volume rendering36, based on manual selection of the relevant structures in the CT images (Fig. 2, Supplementary Data 1, 2 and 3). Detailed descriptions of all procedures, from harvesting the petrosal bones to the digitization of the membranous labyrinth, are given in the Methods part.


Assessing morphology and function of the semicircular duct system: introducing new in-situ visualization and software toolbox
Raw visualizations of stained membranous labyrinths through micro-CT scanning.(a–g) Soft-tissues structures contained inside the bony labyrinth of the human (c,d), rhesus macaque (b,e,g) and squirrel monkey (a,f) specimens. Aa, Ap, Al, anterior, posterior and lateral ampullae, respectively; Ca, Cl, anterior and lateral cupulae (artificially shrunk); CC, common crus; CD, cochlear duct; Cra, Crp, Crl, anterior, posterior and lateral cristae ampullares; S, sacculus; Sa, Sp, Sl, slender parts of the anterior, posterior and lateral semicircular ducts; Sm, macula sacculi; ST, scala tympani; SV, scala vestibuli; Ua, anterior utriculus; Um, macula utriculi. Scale bar is 0.5 mm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5015051&req=5

f1: Raw visualizations of stained membranous labyrinths through micro-CT scanning.(a–g) Soft-tissues structures contained inside the bony labyrinth of the human (c,d), rhesus macaque (b,e,g) and squirrel monkey (a,f) specimens. Aa, Ap, Al, anterior, posterior and lateral ampullae, respectively; Ca, Cl, anterior and lateral cupulae (artificially shrunk); CC, common crus; CD, cochlear duct; Cra, Crp, Crl, anterior, posterior and lateral cristae ampullares; S, sacculus; Sa, Sp, Sl, slender parts of the anterior, posterior and lateral semicircular ducts; Sm, macula sacculi; ST, scala tympani; SV, scala vestibuli; Ua, anterior utriculus; Um, macula utriculi. Scale bar is 0.5 mm.
Mentions: We found that all parts of the semicircular duct system, including the ducts, utricle, ampullae, and cupulae, can be successfully visualized with micro-CT after staining with phosphotungstic acid (PTA)33 (Fig. 1) Tissue fixation should happen within a few days after death, preferably using Bouin solution, and a specimen should not have been frozen as this invariably destroys the delicate membranous labyrinth. Visualization with micro-CT requires a voxel size of less than 20 μm, and a scanning protocol which provides the best available image quality, low noise levels in particular. The most productive approach for 3D visualization and digital quantification of the membranous labyrinth, including the semicircular duct system, is by surface rendering rather than volume rendering36, based on manual selection of the relevant structures in the CT images (Fig. 2, Supplementary Data 1, 2 and 3). Detailed descriptions of all procedures, from harvesting the petrosal bones to the digitization of the membranous labyrinth, are given in the Methods part.

View Article: PubMed Central - PubMed

ABSTRACT

The semicircular duct system is part of the sensory organ of balance and essential for navigation and spatial awareness in vertebrates. Its function in detecting head rotations has been modelled with increasing sophistication, but the biomechanics of actual semicircular duct systems has rarely been analyzed, foremost because the fragile membranous structures in the inner ear are hard to visualize undistorted and in full. Here we present a new, easy-to-apply and non-invasive method for three-dimensional in-situ visualization and quantification of the semicircular duct system, using X-ray micro tomography and tissue staining with phosphotungstic acid. Moreover, we introduce Ariadne, a software toolbox which provides comprehensive and improved morphological and functional analysis of any visualized duct system. We demonstrate the potential of these methods by presenting results for the duct system of humans, the squirrel monkey and the rhesus macaque, making comparisons with past results from neurophysiological, oculometric and biomechanical studies. Ariadne is freely available at http://www.earbank.org.

No MeSH data available.


Related in: MedlinePlus