Functional aspects of carbohydrate complex of the statoconial membrane of the guinea pig utricular macula.

A functional aspect of the carbohydrate complex of the statoconial membrane of the guinea pig utricular macula was observed by the use of the lectins as well as the ruthenium red staining techniques. The ruthenium red staining technique visualized the whole structure of the statoconial membrane as well as the contact zone between the sensory epithelium and the statoconial membrane. The statoconial membrane is composed of the otoconial layer, gelatinous layer, and subcupular meshwork. The otoconial layer was interconnected with sensory epithelium by the gelatinous layer and subcupular meshwork which formed honeycomb structure and housed the sensory hair bundle. This may allow the free movement of the sensory hair bundle. The gelatinous layer and the subcupular meshwork contain N-acetylglucosamine, mannose, and galactose which form acidic mucopolysaccharide and glycoprotein. It has been indicated that these carbohydrate complex may play an important role for the mechanical coupling not only between the statoconial membrane and the sensory epithelium but also between the sensory hair bundle and the statoconial membrane.

Aberrant elemental composition of otoconia in the dancer mouse mutant with a semidominant gene causing a morphogenetic type of inner ear defect.

The elemental composition of otoconia from Jerker and Dancer mouse mutants was analysed in both maculae. A normal elemental content was found in otoconia from Jerker mutants, whereas in the Dancer mutant a large number of otoconia from both maculae contained very high concentrations of phosphorus. In these otoconia, the phosphorus calcium ratio was approximately 1:8, in Jerker (and normal) otoconia approximately 1:150-200. However, otoconia from Dancer mutants occurred with also a normal elemental composition. The increasing content of phosphorus in otoconia may possibly indicate an early onset of aging, i.e. corresponding to a phosphatization process as described in aging human otoconia.

X-ray microanalytic studies on developing otoconia.

The onset of otoconial development in the macula utriculi in CBA/CBA mice occurs on the fifteenth and sixteenth gestational days. Our study was concentrated on the early secretion of calcium in the areas of otoconial formation. The epithelial origin of otoconia is documented. Protrusions from supporting cells in the utricular and saccular epithelia contain very large quantities of calcium in addition to the normal cytoplasmic content of elements. The cell protrusions have an elemental composition clearly differing from that of otoconia as well as from neighbouring utricular cells with protrusions. A directed flow of calcium to developing otoconia from the supporting cells of the maculae is suggested.

Ultrastructural changes of statoconia after segmentation of the otolithic membrane.

The chick vestibule transformed from a homogeneous epithelial layer at day 2 (stage 15) into a pseudo-stratified epithelial layer at day 4 (stage 24). The apical columnal appearance of sensory cells was evident by day 6 (stage 29). In the supporting cells of the saccule and utricle large rough endoplasmic reticulum cisterns filled with material similar to the primitive organic matrix. Fibrillar material of the otolithic membrane remained attached to the supporting cells and accumulated over the saccule and utricle. The primitive otolithic membrane acquired stress-like lines and statoconial units emerged from the upper surface without a central core. Statoconia thickened at the periphery and a central core formed. Calcium was deposited between the fibrils of older statoconia which were located on top of the segmenting membrane. DIAMOX inhibited statoconia formation and/or prevented calcium and the matrix from associating. Large statoconia (100-200 microns diameter) were formed in embryos injected with this carbonic anhydrase inhibitor. Gel electrophoresis of immature statoconial complexes yielded at least 5 major protein bands between 25 and 210 kDa. Ouabain-sensitive potassium-dependent p-nitrophenylphosphatase activity was demonstrated in the endolymphatic sac of newly hatched chicks.

Otoconial mineralization in post-natal development.

Otoconial mineralization has been studied in the utricle of post-natal rats, i.e. from birth to the 20th day. Calcium microanalytically detected is seen to decrease progressively until, after 20 days, when the level is rather lower than at birth. In the adult animal the calcium value is much higher, which leads us to believe that there is an immediate calcium loss that is later recovered. Calcium in the peripheral areas of the macula is proportionately less than in the central part.

Comparative crystallography of vertebrate otoconia.

Otoconial material was obtained from a number of vertebrates to determine the CaCO3 polymorph present. Otoconia and otoliths from bony fish, amphibians, and reptiles are primarily aragonitic; those from birds and mammals are calcitic. This paper summarizes data from all other investigators as well as presenting new data, particularly pertaining to reptiles. The significance, if any, of the relationship between taxonomic group and carbonate polymorph remains an intriguing question.

A re-examination of otoconia from the Shaker mouse.

We have studied saccular and utricular otoconia from Shaker-1 and Shaker-2 mice by X-ray diffraction and scanning electron microscopy. In contrast to previous reports, we found that the crystals were composed of calcite rather than polycrystalline hydroxylapatite. These crystals were indistinguishable mineralogically and morphologically from normal mouse otoconia. The reported occurrence of hydroxylapatite otoconia in the Shaker mouse is probably false.

Microprobe analysis of human otoconia.

Utricular and saccular otoconia (N = 510) from 1 fetus (39th gestational week; Trisomy-18), 2 babies (1 1/2 and 2 months) and 3 adults (58, 61 and 77 years) were analysed with an energy dispersive X-ray microprobe. In all otoconia the elemental composition showed an extremely high concentration of Ca but also Na, Mg, P, S, Cl and K were identified. The presence of non-Ca elements was interpreted as being due to a protein nucleus of the otoconia. Non-Ca elements are more prominent during fetal age and early post-natally than later in life. Old age otoconia contained high concentrations of P which indicates that a ' phosphatization ' of aging otoconia occurs, i.e. calcite otoconia are transformed in situ into apatite by reaction with phosphate ions. The elemental composition of otoconia in Trisomy-18 was similar to that in early postnatal inner ears.

Qualitative and quantitative analysis of otoconia in the normal and in the genetically deaf inner ear.

By using the energy dispersive x-ray microanalysis technique the elemental composition of otoconia was analyzed in the normal fetal and normal adult, Shaker-1 and Shaker-2 mouse. There are no statistically significant differences in Ca concentration between otoconia seen in normal nineteenth gestational day (CBA/CBA) fetuses and that seen in 2-month-old animals. However, the standard deviation is almost three times larger in fetal than in adult otoconia. In all analyses, in both normal and mutant species, the following, elements were identified: Na, Mg, P, S, Cl, K, and Ca. The present findings strongly indicate a calcite composition of otoconia in both normal and mutant species. Significant differences in Ca concentration (p less than 0.05) occurred between the central and peripheral parts of large otoconia in normal mice. No difference in the elemental composition of otoconia in adult normal and Sh-2 mutants was detected. Differences occurred between adult normal and Sh-1 otoconia (Na--p less than 0.05; Mg--p less than 0.001; K--p less than 0.001; Ca--p less than 0.02). It is, however, unlikely that the shaking-waltzing behavior of Sh-1 and Sh-2 mutants derives from a minimal derangement of the elemental composition of otoconia.

Calcite in the statoconia of amphibians: a detailed analysis in the frog Rana esculenta.

The otoconia of Amphibia, especially of the frog Rana esculenta, were studied by X-ray diffraction and scanning electron microscopy (SEM). The SEM studies showed that the membranous labyrinth of Amphibia contains two populations of crystals, which can easily be distinguished by their forms. The X-ray diffraction data indicated that these two populations consist of calcite and aragonite; the endolymphatic sac, the saccule and the lagena contain aragonite, whereas calcite is only found in the otolithic membrane of the utricle. The genetic and functional significance of the existence of two crystalline forms of calcium carbonate in the membranous labyrinth are discussed.