Tutorial on otoconia

Ear dust (immature otoconia)

This is a transmission electron micrograph of young otoconia (inner ear crystals) after phosphotongstic acid stain (PTA). Later during development, PTA reacts strongly with the fibrils and forms robust electron dense precipitates, by reacting predominantly with glycoproteins. Note change of electron density where the central core of each crystal is located. The central core of each crystal may influence the mass-volume ratio of otoconia-endolymph, and could influence buoyancy of the crystals.

Ear dust (near mature otoconia)

This is a transmission electron micrograph of older otoconia after glutaraldehyde fixation and exposy embeddment. The central core of each crystal may influence the mass-volume ratio of otoconia-endolymph, and could influence buoyancy of the crystals.

Ear dust (Organic matrix)

This is a very high magnification image of the organic matrix of chick otoconia showing subunits aggregation at the nanometer scale. When reacted with calcium binding heavy metals, the subunits become denser and are quickly chelated with EDTA.

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Ear dust (Matrix organization)

At over one half million times the original maginification, the fibrils appear to form repeating units when reacting with PTA. The pattern is however far from organized and departs from the crystallographic diffraction pattern of calcite crystals. In birds and mammals otoconia are predominantly made by calcium carbonate (Rocks).

Ear dust (2FFT-Matrix periodicity)

Using different techniques, the author showed that otoconia matrix fibrils are organized in different directions ( (High resolution of Otoconia in Publications). The changing direction of the fibrils contribute the bend that is necessary to form the hexogonal angles, and the central core of the the crystals. While the disparity between the apperance of the fresh and fixed otoconia matrix prevails, newer techniqes (e.g., AFM) corroborated the authors finding about subunits. Unfortunately, recent AFM work fail to clarify the contribution that the elliptical tip of the AFM probe had toward the resulting subunits described.

Explanation

Fig.1 shows that fibrils' packing change toward the central core the corresponding periodicity is shown in Fig. 2. The fibrils do not fallow the regular patters one would expect from the perfect crystallographic projections of the unfixed otoconia. Fig.3 shows cross-over plane of the fibrils (note scale), and the 2FFT patterns for each condition. The insert shows nanometer range subunits from unfixed otoconia.

Ear dust (Cross section of fibrils)

In cross section the fibrils seems to aggregate in patches that yield regular FFT projection that may correspond to the subunits already described in this and other labs (check list of publication and authors curricullum vitae for more information).

Ear dust (Normanski- Birefringency)

The crystallographic projections of otoconia also produce strong biofringency seen under here Normanski interference contrast microscopy. The central core is apparent, and biofringency changes from the core toward the periphery.

Ear dust (Glycoprotein content)

This is a transmission electron micrograph of an otoconium after pyroantimonate stain. The subunits described previously seem to aggregate near and then integrate into the organic template of the crystals.

Ear dust (Gluey substance)

This is a transmission electron micrograph of young otoconia (inner ear crystals) after phosphotongstic acid stain (PTA). The crystals are held together by a gluey gelatinous subtance that is secreted in the endolymphatic space around the same time that the tectorial membrane forms. However, otoconia calcify but adjacent membranes do not. Coexistance of both masses in a critically controlled ionic medium (endolymph) may involve molecules with multiple functions.

Ear dust (Central Core)

This is a transmission electron micrograph of young otoconia (inner ear crystals) after phosphotongstic acid stain (PTA). Note the characteristic "cat-like" appearance of otoconia in cross section. The central core forms as different planes made by diverging fowing plates meet (see Fermin Micros. Res. Techn 1993).