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PubMed1994

Cytoskeletal organization of the vestibular sensory epithelia: saponin perfusion method for observing intracellular structures by scanning electron microscopy.

The cytoskeletal organization of the guinea pig vestibular sensory epithelial cells were investigated by the use of saponin perfusion method using scanning electron microscopy. The skeletal framework of a cell is composed of thin (actin or intermediate filaments) and thick filaments (microtubules). The membrane bound organelles such as nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, etc. were also well demonstrated. This made it possible to investigate the three-dimensional structures of cytoskeletons as well as their complex interactions with various membranes bound organelles. It is therefore suspected that this technique may provide us further information about distribution, topographic relationships, and the functional role of cytoskeletons.

Actin Cytoskeleton↗
PubMed1984

The mormyrid brainstem. I. Distribution of brainstem neurones projecting to the spinal cord in Gnathonemus petersii. An HRP study.

The sources of the descending spinal tracts were identified in the teleost fish Gnathonemus petersii by retrograde HRP transport. HRP injections were made at two spinal levels, either at level of the caudal end of the dorsal fin, anterior to the electric organ, or at the pectoral fin. In both cases all labeled cells were found in the rhombencephalon and the mesencephalic tegmentum. No labeled cells were observed either in the cerebellum and lateral line lobes or in the dorsal mesencephalon i.e. torus semicircularis and mesencephalic tectum or in the telencephalon. Following caudal spinal injections, the majority of the labeled cells were grouped in a median and a ventrolateral column of the rhombencephalic reticular formation. The latter is composed of three parts corresponding to the nucleus reticularis inferior, medius and superior. Both Mauthner cells, all the cells in the medullary relay nucleus controlling the electric organ discharge and a few cells in the posterior part of the magnocellular octaval nucleus were labeled. In the mesencephalon, four nuclei were identified by HRP labeling: the nucleus of the medial longitudinal fasciculus, the nucleus reticularis mesencephali and the anterior and posterior tegmental mesodiencephalic nuclei. The rostral injections revealed several additional spinal projections from the descending vestibular and tangential nuclei, from the medial part of the magnocellular nucleus and, finally, from the rostral periventricular gray of the mesencephalon. Also, after such injections, a greater number of cells were labeled in the reticular formation, especially in the median column and in the inferior reticular nucleus. The results suggest that the rostral spinal cord has a larger connection with the acoustico-vestibular area and the medullary reticular formation than the caudal spinal cord. In contrast, the mesencephalic nuclei, probably linked to the mesencephalic tectum and the pretectal area, appears to be a coordinating apparatus between the visual system and the trunk/tail musculature. Thus, it appears that teleost fish possess the same basic equipment of descending spinal pathways as higher vertebrates.

Animals↗
PubMed1994

Ultrastructure of melanocytes in the dark cell area of human vestibular organs: functional implications of gap junctions, isolated cilia, and annulate lamellae.

BACKGROUND: It is known that melanocytes exist in almost all parts of the inner ear, such as the cochlear duct, stria vascularis, Reissner's membrane, modiolus, vestibular organs in the region surrounding the cristae and maculae, semicircular canals, and pars rugosa of the endolymphatic sac. But there have been few studies using human materials, because of the difficulty of obtaining materials. We attempted to investigate the detailed ultrastructure of melanocytes in the vestibular organs of human inner ear. METHODS: Eight surgical specimens obtained from patients with vestibular schwannoma were studied by light microscopy and electron microscopy. RESULTS: Melanocytes were found in the subepithelial layer of the dark cell area. Melanocytes had round or spindle-shaped nuclei and clear cytoplasm with brown pigment granules. Besides melanocytes, there were melanophages, fibroblasts, and small blood vessels. Through electron microscopy we found melanocytes with round-shaped melanosomes in various stages of pigmentation, well-developed Golgi apparatus and endoplasmic reticulum in the cytoplasm, and many cytoplasmic processes. Gap junctions were occasionally found between the cytoplasmic processes. And there were pinocytotic vesicles just under the limiting membrane of melanocytes, and intermediate filaments were abundant in the cytoplasm. Isolated cilia of melanocytes, annulate lamellae, and fusiform banded structures in the connective tissue area around melanocytes were found. CONCLUSIONS: Melanocytes in human vestibular organs actively synthesize melanosomes. Frequent findings of isolated cilia and fusiform banded structures and the incidental existence of annulate lamellae may be an indicator of this metabolically activated state of melanocytes. Moreover, monitoring environmental changes by isolated cilia, melanocytes in the human inner ear could act not only as one cell but also as a group to achieve their physiological functions by means of information transmission through gap junctions.

Adult↗
PubMed1999

[Tinnitus during headache: clinical-instrumental evaluation].

During the five years running from December 1993 to January 1998, 112 patients who had come to our University Clinic suffering from headache were examined. From this group 71 complaining of tinnitus during headache were recruited for the study: 19 patients suffered from migraine without aura, 8 migraine with aura, 15 tension headache, 21 mixed headache, 3 basic migraine and 5 cluster headache. The purpose of this work was to determine the incidence and to identify the frequency of the various types of tinnitus in the study sample. Once cardiovascular and metabolic pathologies, previous cranial or cervical traumas, barotrauma, chronic on-the-job noise exposure, cervical arthritis, ATM malocclusion, use of drugs that damage the hearing apparatus, morbose processes of the external and middle ear, otosclerosis, jugular tympanum paraganglioma, Meniere's disease, acoustic neurinoma were all ruled out, the patients underwent the following battery of instrumental tests: tonal audiometry, impedance measurement, vestibular examination, electronystagmography, ABR, simplified tinnitometry. Only those patients with normal hearing underwent the tinnitometry and, therefore, the type of tinnitus was established only for this group of 53 patients. Tinnitometry showed that 37% of these subjects had tinnitus at the higher frequency tones, 11% at the middle frequencies, 29% complained of tinnitus at the lower frequencies while 23% complained that the bothersome buzzing was a compound noise. In addition, the subjective intensity of the tinnitus was analyzed. The authors devised a tinnitus irritation scale covering a range from 0 (not irritating) to 10 (intolerable). The tinnitus was bilateral in 66% of the cases while it was limited to only one ear in the remaining 34%. In 15% of the cases tinnitus was present even when there was no headache. In the literature, the etiopathogenesis of tinnitus associated with migraine headache has been attributed to vascular and neuropeptide mechanisms. Even the psychological component appears to play a role in triggering the event. These hypotheses deserve more in depth study.

Adolescent↗
PubMed1997

Co-administration of the neurotrophic ACTH(4-9) analogue, ORG 2766, may reduce the cochleotoxic effects of cisplatin.

In this study the effect of the neurotrophic ACTH(4-9) analogue, ORG 2766, on cisplatin cochleotoxicity was investigated with both light- and transmission electron microscopy. Guinea pigs were treated with either cisplatin+ORG 2766 (n = 11) or cisplatin + physiological saline (n = 9). All animals treated with cisplatin + physiological saline showed complete loss of outer hair cells (OHC) and degeneration of the organ of Corti in the basal cochlear turns, while partial OHC loss was found in the middle and apical turns. The inner hair cells (IHC) and other cochlear tissues were not affected. Eight animals from the group treated with cisplatin + ORG 2766 demonstrated similar pathological changes, but to a lesser degree, especially in the middle turns. The three remaining animals demonstrated no cochlear alterations at all, light-microscopically, and only minor subcellular changes in the OHCs at the ultrastructural level. Electrophysiologically, these three animals showed normals compound action potential (CAP) amplitudes at stimulus frequencies from 0.5 to 16 kHz and normal cochlear microphonics (CM) in the frequency range from 0.5 to 8 kHz. The other animals treated with cisplatin + ORG 2766 showed a severe loss in their CAPs and CM, except for one showing intermediate loss. All animals from the group treated with cisplatin alone showed a severe loss in their CAPs and CM. Endolymphatic hydrops was present in all animals from the cisplatin- and the cisplatin + ORG 2766-treated groups. These data indicate that daily, concomitant administration of ORG 2766 may reduce OHC loss and subsequent degeneration of the organ of Corti in cisplatin-treated guinea pig cochleas.

Acoustic Stimulation↗
PubMed1987

Cupulogenesis and glycoconjugates in the labyrinthine ampulla as revealed by WGA-gold labeling.

We studied the distribution of wheat germ agglutinin (WGA)-bindable glycoconjugates in the vestibular ampulla of mongolian gerbils. WGA was conjugated with gold particles and applied to Lowicryl K4M sections of the ampulla. WGA-binding sites were found on the cupula and some of the secretory granules and Golgi apparatuses in the supporting cells of the sensory epithelia. The granules were seen to secrete into the endolymphatic space through reticular membrane. It is likely, therefore, that glycoconjugates are glycosylated at the Golgi apparatus in the supporting cells, stored in the granules, and secreted through the reticular membrane into the endolymphatic space to be used as a component of the cupula. The cell membranes of various cells, connective tissue filaments in the perilymphatic space and the cytoplasm of melanocytes were also labeled with WGA-gold.

Animals↗
PubMed2006

Triple semicircular canal occlusion in guinea pigs with endolymphatic hydrops.

HYPOTHESIS: Triple semicircular canal occlusion will eliminate rotatory stimulation to the vestibular peripheral system (as it blocks endolymphatic fluid movement) and therefore release rotatory vertigo attack. This surgery is safe in ears with endolymphatic hydrops. BACKGROUND: Semicircular canal occlusion has been used as an alternative treatment of intractable benign paroxysmal positional vertigo with varied success. Triple semicircular canal occlusion in animal models blocks the responses of the semicircular canals to rotation and spares cochleae and the otolithic apparatus. This result suggests that triple semicircular canal occlusion is a prospective method in vertigo management for patients with Ménière's disease. However, the effectiveness and safety of triple semicircular canal occlusion has not been fully evaluated in ears with endolymphatic hydrops. METHODS: Endolymphatic hydrops was established in 20 guinea pigs by endolymphatic sac obliteration. Triple semicircular canal occlusion was performed in 12 of them 120 days after endolymphatic hydrops surgery, whereas 8 others were killed for morphologic observation to confirm endolymphatic hydrops. Auditory and vestibular functions were monitored from the time before endolymphatic hydrops until 1 month after triple semicircular canal occlusion. Endolymphatic hydrops and canal occlusion were confirmed by morphologic observation. RESULTS: Successful establishment of endolymphatic hydrops was indicated by mild elevation of the auditory brainstem response threshold and tentative asymmetry in nystagmus. Endolymphatic hydrops was confirmed by cochlear morphology in all eight animals that were killed 120 days after endolymphatic hydrops surgery. After triple semicircular canal occlusion, all 12 animals showed spontaneous nystagmus with a slow component toward the side that had been operated on, head tilt, rotated walking, and tentative asymmetry in rotatory nystagmus. The static symptoms disappeared within 1 month after triple semicircular canal occlusion. Caloric nystagmus was only slightly reduced after endolymphatic hydrops as compared with the contralateral ears but could not be elicited at all after triple semicircular canal occlusion. No significant elevation in auditory brainstem response threshold was found after triple semicircular canal occlusion. The canal occlusion and endolymphatic hydrops were confirmed in all surgical ears. CONCLUSION: Triple semicircular canal occlusion is effective for eliminating the response of semicircular canals to rotation and caloric stimulation and is safe in ears with endolymphatic hydrops. Also, the static compensation to the disequilibrium is quick and complete. These results suggest that triple semicircular canal occlusion should be an option for controlling rotatory vertigo in Ménière's disease.

Animals↗
PubMed1992

Effect of head orientation on the diagnostic sensitivity of posturography in patients with compensated unilateral lesions.

Patients with compensated unilateral vestibular lesions often have no detectable abnormality on conventional posturography. The purpose of this study was to determine whether a change in head orientation could improve the diagnostic sensitivity of the test for these patients. Twenty-four patients with known unilateral vestibulopathy and twenty-four normal controls were tested on the EquiTest apparatus in four head positions: head centered, head tilted right, head tilted left, and head extended. The sensory organization test was performed for each head position, using a single trial for each sensory condition. The test sequence was randomized to account for simple order effects. The subject's equilibrium was quantified by a performance index and a composite score of all sensory conditions was calculated for each head position. Patients with unilateral vestibulopathy had more postural sway with the head tilted contralateral to the side of lesion. The difference between the mean composite scores for ipsilateral and contralateral head tilts was statistically significant (p less than 0.05). When individual trials were compared, equilibrium scores were significantly different only for sensory conditions that required vestibular input. Head extension increased postural sway in both patients and controls. Equilibrium scores were significantly different for all sensory conditions in which the support was sway-referenced. We suggest that the results of head extension in patients are similar to those found in normal individuals.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Three-dimensional structures of the vestibular sensory epithelia.

Vestibular neurosensory epithelia of the guinea pig and the bull frog were investigated by scanning electron microscopy. The crista ampullaris or macula were freeze fractured followed by maceration with 0.1% OsO4 solution for 24-60 h (osmium-DMSO-osmium method). Following this, three-dimensional intracellular structures were observed. The mitochondria which exist in the nerve chalice surrounding the type I cell were various in shape, globular, long and slender. Golgi apparatus, endoplasmic reticulum and thin fibrous structures of the sensory cells or supporting cells were clearly demonstrated. Concerning nervous system, nerve fibre, afferent and efferent nerve endings, further synaptic structures were also observed stereoscopically.

Acoustic Maculae↗
PubMed2006

Evidence for positive force feedback during involuntary aftercontractions.

We examined the involuntary isotonic muscle aftercontraction which follows a 1-min voluntary contraction at 60% of maximum voluntary force. Aftercontractions provide a unique paradigm for investigating the automatic postural control of the upper limb in man. Previous work has shown that the strength of these contractions in m. deltoid is linearly dependent on the inclination of the subject's body in the gravitational field. The current experiments were designed to test if this was due to the gravitational loading on the arm as this also changes with body inclination. The subject sat with the head stationary to prevent changes in vestibular orientation. Aftercontractions in m. deltoid were evoked with the normal weight of the arm present and also with arm loadings equal to 0, 25, 50 and 75% of this value. These reductions were produced by a counter lever apparatus. The results showed that the EMG amplitude of this involuntary contraction depended linearly on the loading of the arm. This is interpreted as being the result of positive load feedback. Aftercontraction EMG amplitude at 100% load was 2.7 times greater than at 0% load. The results are discussed in the context of recent work on positive load feedback in man and animals.

Adult↗
PubMedDate not supplied

Development of vestibular receptor surfaces in human fetuses.

The development of human vestibular receptors was studied between the 7th and 14th gestational weeks using scanning electron microscopy. The development phase appeared to last longer than previously described. At 7 weeks, no receptors were individualized, the vestibular epithelium was plicated, and scarce nascent hair bundles could be seen grouped in a small area. At 8 weeks, all receptors were well differentiated. Modifications in crista shapes were evaluated qualitatively and quantitatively along the length of their profile. Their growth occurred in two quick steps with a pause between the 9th and 12th weeks, during which growth slowed and a transformation occurred. In the utricle, the epithelium decreased in thickness, and this process underwent a pause between the 8th and 11th weeks. These results demonstrate pauses in the maturation process of the vestibular receptors and show that the utricles develop one week in advance of the cristae. At 14 weeks, all receptors had an adult profile, but the cristae had only reached 55 per cent of their adult size. The ciliary apparatus appeared to be nearly mature in the utricle but was still growing in the cristae. The differentiation of ciliary tufts in the cristae displayed an apex-base gradient. These developmental patterns were compared with those described in the mouse.

Adult↗
PubMed1994

Cytoskeletal organization of the vestibular supporting cells. Saponin perfusion method for observing intracellular structures by scanning electron microscopy.

The cytoskeletal organization of the guinea pig vestibular supporting cells was investigated employing the saponin perfusion method using scanning electron microscopy. The skeletal framework of a cell was composed of actin, intermediate filaments and microtubules. The membrane bound organelles such as nucleus mitochondria, endoplasmic reticulum, Golgi apparatus, etc. were also well documented. This made it possible to investigate the three-dimensional organization of cytoskeletons as well as their complex interaction with various membrane bound organelles. The intermediate filaments were usually seen surrounding the nucleus and extending through the cytoplasm which connected the nuclear membrane to the plasma membrane, reticular lamina or other cytoorganelles. The intermediate filaments also closely related to the desmosomes. These findings suggest that the intermediate filaments provide mechanical support to the cell and its nucleus. The microtubules were closely related to the secretory granules, Golgi apparatus and intermediate filaments, which supports the idea that the microtubules may control the distribution of intermediate filaments, and also play an important role for the transport of the secretory granules.

Actins↗
PubMed1991

Effect of gentamicin on vestibular ganglion.

The morphological changes of the vestibular ganglion induced by gentamicin (GM) were investigated using light, scanning and transmission electron microscopy. The guinea pigs were injected 4 mg of GM into the middle ear for 5 days. The vestibular ganglion was observed up to 4 weeks after the treatment. Three days after the treatment the degenerative change was first noted in the vestibular ganglion. The degenerative process started from the destruction of mitochondrial cristae and vacuolization of the cytoplasm of the Schwann cell. The cytoplasmic organelles in the ganglion cell gradually deteriorated with swelling of the endoplasmic cisterns as well as Golgi apparatus. At the later stage, the myelin sheath around the ganglion cell disappeared and the number of the cells reduced. These changes of the ganglion cell may be due to the direct action of GM.

Animals↗
PubMed1998

Genetic analysis of vertebrate sensory hair cell mechanosensation: the zebrafish circler mutants.

The molecular basis of sensory hair cell mechanotransduction is largely unknown. In order to identify genes that are essential for mechanosensory hair cell function, we characterized a group of recently isolated zebrafish motility mutants. These mutants are defective in balance and swim in circles but have no obvious morphological defects. We examined the mutants using calcium imaging of acoustic-vibrational and tactile escape responses, high resolution microscopy of sensory neuroepithelia in live larvae, and recordings of extracellular hair cell potentials (microphonics). Based on the analyses, we have identified several classes of genes. Mutations in sputnik and mariner affect hair bundle integrity. Mutant astronaut and cosmonaut hair cells have relatively normal microphonics and thus appear to affect events downstream of mechanotransduction. Mutant orbiter, mercury, and gemini larvae have normal hair cell morphology and yet do not respond to acoustic-vibrational stimuli. The microphonics of lateral line hair cells of orbiter, mercury, and gemini larvae are absent or strongly reduced. Therefore, these genes may encode components of the transduction apparatus.

Acoustic Stimulation↗
PubMed1995

Cytoskeletal organization of the vestibular sensory epithelia.

The cytoskeletal organization of the guinea pig vestibular sensory epithelium was investigated by employing the saponin perfusion method and scanning electron microscopy. The skeletal framework of a a cell was found to consist of actin, intermediate filaments and microtubules. The membrane-bound organelles such as nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, etc. were also well documented. This made it possible to investigate the three-dimensional organization of cytoskeletons as well as their complex interaction with various membrane-bound organelles. The intermediate filaments were demonstrated not only in the supporting cells but also in the sensory cells. They are usually seen surrounding the nucleus and extending through the cytoplasm which connects the nuclear membrane to the plasma membrane, cuticular plate, reticular lamina or other cyto-organelles. The intermediate filaments are also closely related to the desmosomes. These findings suggest that the intermediate filaments provide mechanical support to the cell and its nucleus. In the sensory cells, microtubules are found mainly in the supranuclear portion of the cells, running parallel to the main axis of the cell body, which is directly connected to the cuticular plate. These findings suggest that the microtubules provide the cell with mechanical support and may be closely related to the sensory cell transduction system. Inside the supporting cells, the microtubules are closely related to the secretory granules, Golgi apparatus and intermediate filaments, which supports the idea that the microtubules may control the distribution of intermediate filaments, and also play an important role for transport of the secretory granules.

Animals↗