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Results for “Otolithic Membrane”

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15 recordsLinked to original sources
PubMed1979

Incorporation of radioactive calcium into otolithic membranes of the guinea pig after aminoglycoside treatment.

The influence of neomycin and streptomycin on the calcium metabolism of the otolithic membranes was investigated in the guinea pig. After chronic treatment with either drug, animals were injected intraperitoneally with radioactive calcium. Retention of calcium in the serum was unaffected by drug treatment, as was the incorporation of radioactivity into bone (femur and otic capsule). Both drugs inhibited the calcium uptake into saccular and utricular otolithic membranes by 30 to 40%.

Animals↗
PubMedDate not supplied

Incorporation of radioactive calcium into otolithic membranes and middle ear ossicles of the gerbil.

45CaCl2 was injected into gerbils in single or multiple doses, and the resulting radioactivity in serum, otoconial CaCO3, bone samples, and selected labyrinthine epithelium was determined by liquid scintillation spectrometry. Incorporation into both utricular and saccular otoconia occurred at the rate of 0.06-0.07 nmole Ca++ per day, corresponding to a fractional rate of uptake of 0.1%. The retention of radioactivity had a half-life of approximately 11 days. The rate of incorporation of calcium for the middle ear ossicles was 5-7 times that for otoconia and was similar to that for otic capsule and skeletal bone. The level of 45Ca++ was higher in the pigmented regions of the utricular membranous wall than in the non-pigmented areas of the utricular and ampullary wall and in the stria vascularis.

Animals↗
PubMed1992

The statoconial membrane of the guinea pig utricular macula. Scanning electron microscopic investigation combined with the freeze-fracturing technique.

The superstructure of the guinea pig utricular macula was investigated using scanning electron microscopy combined with the freeze-fracturing technique. The statoconial membrane was composed of the otoconial layer, otolithic membrane and subcupular meshwork. The otolithic membrane consisted of closely arranged filaments with beaded appearance and densely packed globular matrix near the otoconial layer. The subcupular meshwork consisted of long branching filaments cross-bridged to one another. The filaments were continuous with those of the otolithic membrane on one side and with the surface of the epithelium on the other, which fills the space between the otolithic membrane and the macular surface. The otolithic membrane would function as a rigid plate and equally distribute the shear force of the otoconial layer to all the ciliary bundles. The subcupular meshwork may play an important role in transmitting the shear strain of the otolithic membrane to all the ciliary bundles and may also exert an additional dampening effect to prevent unwanted vibration.

Acoustic Maculae↗
PubMed1979

A transmission and scanning electron microscopic study of the saccule in five species of catfishes.

The sacculi of five species of catfishes were studied by transmission and scanning electron microscopy. In four species, the sagitta exhibited a multifluted anterior part and a tapered posterior part; in Corydoras aeneus, however, the fluted part was absent, and a vertical component extended dorsally to terminate near the opening of the transverse canal. In all species, the otoliths had a laminar structure. An otolithic membrane was present, and hair cell bundles projected into cavities on the macular surface of the membrane. Attachments of the otolithic membrane to the neuroepithelium included short extensions of the membrane to the tallest components of the hair cell bundles of the peripheral cells and more delicate connections to the kinocilium and taller stereocilia of central cells; in addition, attachments to the microvilli of supporting cells were present. In both hair cells and supporting cells single microtubules and bundles of microtubules were present; the bundles had an orderly arrangement and were associated with cytoplasmic densities surrounding the desmosomes. The hair cells were innervated by both afferent and efferent nerve endings. Studies of the polarization of the hair cells in all species (except C. aeneus) showed that there was a single longitudinal axis that divided dorsally polarized cells from those oriented ventrally. In Doras spinosissimus and Bunocephalus bicolor, an additional line of polarization was evident in a small area in the anterior part of the macula; therefore, in these forms there was a double bipolar orientation.

Animals↗
PubMed1976

[The development OF THE vestibular apparatus under conditions of weightlessness].

The spawn of the aquarium fish Brachydanio rerio was developing during 5--6 days under conditions of weightlessness (first on board the spaceship "Sojuz-16", then in the space station "Salut-4") in special aquariums "EMKON", in thermostable installations. Electron microscopically the embryos were found to have a well developed labyrinth in early developmental histologically and cytologically differentiated receptory structures of the macula utriculi and macula saccili. In contrast to controls, the experimental animals showed certain alterations in the otolite organization. In similar experiments the embryos of clawed frog Xenopus laevis in the stage of the tail bud were also placed in special containers "EMKON" and thermostable apparatus "Biotherm-4" and by the spaceship "Sojuz-17" were brought to the space station "Salut-4", where it stayed for 16 days. The initial embryos had already had a well developed acoustic vesicle with macula communis. Inspite of the preliminary load by start acceleration and staying under conditions of weightlessness, they reached the general development fairly similar to controls. As it was shown electron microscopically their labyrinth had highly histologically and cytologically differentiated structures. However, a disturbance of the development of the otolithic membrane and otoconia should be noted. The alterations observed in the otolithic membrane organization in experimental fishes and frogs may be explained by general disorders in calcium metabolism.

Animals↗
PubMedDate not supplied

Metabolic disorder of otoconia after streptomycin intoxication.

Little is known about the origin or the metabolism of otoconia. Streptomycin sulfate was found to cause a decrease in their number on the otolithic membrane of the utricle and saccule in guinea pigs. The remaining otoconia on the otolithic membrane varied in shape and size and giant otoconia with multilayered arrangement were observed by means of a scanning electron microscope. These otoconia contained the normal amount of calcium in the form of standard calcium calcite crystal. The lost otoconia were found attached to the surface of some vestibular dark cells. Otoconia in this new position were irregular, shrunken or fragmented. Their calcium content, measured with an X-ray micro-analyzer, was variably diminished. The dark cells appeared to be actively engaged in absorption of calcium ions, from the attached otoconia. The dark cell is considered to be a receptacle for the disposal of otoconia.

Animals↗
PubMed1992

The response of statocyst receptors of the lobster, Homarus americanus, to movements of statolith hairs.

1. While recording from the statocyst nerve of Homarus americanus, we deflected the statolith hairs from the "rest" position they assumed after the lith was removed. 2. Each of the smaller statocyst hairs apparently drove three sensory receptors; all receptors were sensitive to hair position, hair movement velocity, and hair movement direction. 3. Two of the receptors, types A and C, only responded when the hair was lifted up and away from rest; the third, type B, only responded vigorously when a hair was moved back toward rest from such a deflexion. 4. Type A and B receptors were phasic-tonic; type C receptors were phasic.

Animals↗
PubMed2026

Selective saccular plasticity under microgravity links peripheral transcriptomic remodeling to postflight vestibular dysfunction.

Long-duration exposure to microgravity disrupts human balance and spatial orientation, yet the molecular mechanisms underlying vestibular adaptation to spaceflight remain poorly understood. Here, we tested the hypothesis that the saccule, the primary gravity-sensing otolith organ, undergoes selective remodeling during spaceflight and contributes to transient postflight postural instability. Using a cross-species approach, we combined transcriptomic analysis of mouse otolith organs with physiological assessments in astronauts. Laser microdissection-based RNA sequencing of mouse otolith sensory epithelia after a 35-d spaceflight revealed pronounced, organ-specific transcriptomic remodeling in the saccule, whereas the utricle remained stable. Principal component and clustering analyses demonstrated that the saccular transcriptome shifted toward an utricle-like profile under microgravity, accompanied by changes in genes related to synaptic and neuronal function. Promoter motif analysis identified NFAT-associated transcriptional networks, suggesting Ca2+-dependent regulation of synaptic plasticity as a potential molecular substrate of gravity-dependent adaptation. In parallel, vestibular testing in astronauts following long-duration missions (157 to 328 d) revealed selective attenuation of saccule-mediated cervical vestibular-evoked myogenic potentials and increased postural sway immediately after return to Earth, while utricle-mediated responses and semicircular canal function were preserved. Both saccular function and postural stability recovered within approximately 10 d. Notably, early postflight postural instability was partially mitigated by noisy galvanic vestibular stimulation, consistent with stochastic resonance-mediated sensory enhancement. Together, these findings identify the saccule as a plastic gravity sensor and establish a mechanistic link between peripheral molecular remodeling and functional balance deficits after spaceflight, providing a framework for developing countermeasures to facilitate vestibular readaptation during human space exploration.

Animals↗
PubMed1992

Modeling 3-D slow phase velocity estimation during off-vertical-axis rotation (OVAR).

Off-vertical-axis rotation (OVAR) in darkness generates continuous compensatory eye velocity. No model has yet been presented that defines the signal processing necessary to estimate head velocity in three dimensions for arbitrary rotations during OVAR. The present study develops a model capable of estimating all 3 components of head velocity in space accurately. It shows that processing of two patterns of otolith activation, one delayed with respect to the other, for each plane of eye movement is not sufficient. (A pattern in this context is an array of signals emanating from the otoliths. Each component of the array is a signal corresponding to a class of otolith hair cells with a given polarization vector as described by Tou and Gonzalez in 1974.) The key result is that estimation of head velocity in space can be achieved by processing three temporally displaced patterns, each representing a sampling of gravity as the head rotates. A vector cross product of differences between pairs of the sampled gravity vectors implements the estimation. An interesting property of this model is that the component of velocity about the axis of rotation reduces to that derived previously using the pattern estimator model described by Raphan and Schnabolk in 1988 and Fanelli et al in 1990. This study suggests that the central nervous system (CNS) maintains a current as well as 2 delayed representations of gravity at every head orientation during rotation. It also suggests that computing vector cross products and implementing delays may be fundamental operations in the CNS for generating orientation information associated with motion.

Head↗
PubMed1976

Inner ear pathologic features following mumps infection. Report of a case in an adult.

Temporal bone studies in an adult with a moderately severe, bilateral sensorineural hearing loss revealed bilateral cochlear changes 13 years after mumps infection. The organ of Corti was completely absent in the greater part of the superior horizontal basal limbs, with occasional hair cell loss throughout the rest of the cochlea. The outer sulcus cell area was degenerated. The stria vascularis was normal, as was the tectorial membrane, except for small hyaline droplets. The number of nerve fibers was extremely decreased in the spiral bony lamina of the basal turns. Basophilic material, possibily representing degeneration of otoliths, was present in the saccule and utricle, bilaterally, with small amounts in all of the ampullae. This was considered to be either a possible result of cytotoxic cancerocidal therapy, or an incidental nonspecific change.

Adult↗
PubMed1977

Effect of otolith end organ ablation on pendular rotation nystagmus in squirrel monkeys.

Damped pendular rotation nystagmus was studied in squirrel monkeys before and after otolith end organ ablation (two-stage operations). After each operation, the nystagmic slow phase eye speed toward the operated side was reduced (to about 73% of that before the operation) and that to the non-operated side did not show any marked change. A few subjects showed spontaneous nystagmus with amphetamine administration but only in dark (could not be found in light) immediately after the operation, and it disappeared rapidly. Therefore, this post-ablative reduction of the slow phase eye speed is considered to result from the loss of inputs from the otolith end organs.

Amphetamine↗