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PubMed2002

Microtubule associated protein (MAP1A) mRNA was up-regulated by hypergravity in the rat inner ear.

Differential display analysis of differential mRNA expression in the rat inner ear under hypergravity identified two down- and four up-regulated genes. The up-regulation of microtubule associated protein 1A (MAP1A) in one of these was confirmed by real-time polymerase chain reaction. Since MAP1A is believed to work as a cell stabilizer connecting the actin with microtubule, this is possibly a response to strengthen this stabilizer under hypergravity. The MAP1A gene is the first found to be affected by gravity change in the inner ear.

Animals↗
PubMed1999

Expression pattern of aquaporin water channels in the inner ear of the rat. The molecular basis for a water regulation system in the endolymphatic sac.

Mammalian aquaporins constitute a family of so far 10 related water channel proteins which mediate osmotically driven water fluxes across the plasma membrane. Because regulation of the ionic composition and osmolality of inner ear fluids is of great functional significance, we investigated the expression patterns of aquaporins in five defined areas of the rat inner ear by RT-PCR. The tissues used were stria vascularis, endolymphatic sac, Reissner's membrane, vestibulum and organ of Corti. Aquaporin 1 transcripts were detected in all tissues and are probably constitutive. Aquaporin 5 was only expressed in the organ of Corti and in Reissner's membrane. We show that aquaporin 2, so far considered to be specific to the principal cells of the renal collecting duct, is expressed in the endolymphatic sac. Aquaporin 2 expression was not detected in any other inner ear region. The postnatal appearance of aquaporin 2 transcripts in the endolymphatic sac resembled that in the kidney, i.e. it increased postnatally until day 4. The full-length DNA for aquaporin 2 was cloned from cDNA of the endolymphatic sac. It had an irrelevant Ile54Thr mutation because it could be functionally expressed in Xenopus oocytes. Also exclusively in the endolymphatic sac of the inner ear, we detected transcripts for aquaporin isoforms 3 and 4 which are known to be expressed in the renal principal cells. In the kidney, aquaporin 2 regulation involves vasopressin-stimulated, cAMP-dependent phosphorylation of Ser256 of aquaporin 2 which is stored in cytosolic vesicles. These storage vesicles also contain a serpentine calcium/polycation-sensing receptor. Vesicle shuffling to the plasma membrane involves proteins such as vesicle-associated membrane protein VAMP2, syntaxin-4 and the small GTPase Rab3a. Using RT-PCR we were able to demonstrate the expression of all of these components. By analogy the data suggest that in the endolymphatic sac of the inner ear a system for cellular water permeability is in place which may share many similarities with that characterized in the principal cells of the renal collecting duct. These findings may have a number of interesting pharmacological implications which need to be addressed in future studies.

Aging↗
PubMed1986

Intermediate filaments in the newborn inner ear of the mouse.

The presence of intermediate filaments in the inner ear of the newborn mouse was analyzed with immunofluorescence techniques using antibodies against the five classes of intermediate filaments: cytokeratins, vimentin, desmin, neurofilaments and glial fibrillary acid protein (GFA). Neurofilaments were found in all nerve fibers from the ganglion cell to the hair cell. In the vestibular ganglion two subpopulations of ganglion cells were identified: a minor part staining intensively with neurofilament and the major part of cells lacking this immunofluorescence. Vimentin occurred in a number of supporting structures in the membranous labyrinth, but not in vestibular or cochlear ganglion cells. Cytokeratins, desmin or GFA were not identified in the inner ear.

Animals↗
PubMed1991

The presence of laminin in the fetal human inner ear.

The expression of laminin was analyzed in the human fetal inner ear using immunohistochemical methods. In the 11-week-old human fetus, the presence of laminin was found in the basement membrane of the immature cochlea, endolymphatic sac and vestibular end organs. The reaction of the basement membrane of the endolymphatic sac was strong in the 15-week-old human fetus. A laminin reaction was seen in the cochlea, Reissner's membrane, epithelial cells of the limbus spiralis, the basilar membrane and the stria vascularis. In particular, the capillaries and basement membrane of the stria vascularis were strongly positive. These results suggest that laminin may be an essential component in the development of the inner ear and may possibly be related to filtration of the endolymph.

Basement Membrane↗
PubMed2000

[Cell proliferation in endolymphatic sac during the immune response of inner ear].

OBJECTIVE: To study the cell proliferation in endolymphatic sac(ES) during the secondary immune response in inner ear. METHODS: Fifteen healthy, female SD rats were employed in the experiment. Sensitized systematically with keyhole limpet hemocyanin (KLH), the animals were inoculated with the same antigen through cochlea basal turn into the labyrinth. Administrated 5-bromo-2'-deoxyuridine (BrdUrd) intraperitoneally, the rats were sacrificed and the temporal bones were harvested at 3, 7, 14 day after labyrinth vaccination respectively. The frozen sections of the decalcified samples were dealt with H-E staining and immunohistochemical methods to investigate the cellular infiltration, BrdUrd and IgG positive cells in the ES. RESULTS: While the ES lumen and perisaccular region were infiltrated with mononuclear-phagocyte at the 3rd day post-vaccination, plasmocyte and lymphatic cells become the predominant infiltrating cells in the ES at the 7th day. The KLH in the ES lumen were phagocytized at the 3-7th day post-vaccination. S-phase cells and IgG positive cells in ES increased markedly in the 3rd day and 7-14 days post-vaccination respectively with similar localization. CONCLUSION: The activity of cell proliferation in the ES enhance and local proliferated cells may differentiate in situ into immunocompetent cells during the secondary immune response against TD antigen in the inner ear. This indicates that ES plays an important role in immune response of inner ear.

Animals↗
PubMed2000

Localization of soluble guanylate cyclase activity in the guinea pig inner ear.

The aim of this study was to characterize the nitric oxide (NO) receptor soluble guanylate cyclase (sGC), to determine the cells targeted by NO and to elucidate the function of the NO/cGMP pathway in the inner ear. sGC activity in the inner ear was localized by immunohistochemical detection of NO-stimulated cGMP. Soluble guanylate cyclase activity in the cochlea was detected in the nerve endings underneath the outer and inner hair cells, supporting cells, stria vascularis and vessels. In the vestibular organs, sGC activity was detected in the cytoplasm of sensory cells, nerve fibres, dark cells and transitional cells and vessels. These findings suggest that the NO/cGMP pathway may be involved in regulatory processes in neurotransmission, blood flow and inner ear fluid homeostasis.

Animals↗
PubMed1996

Inner ear malformations in patients with sensorineural hearing loss: detection with gradient-echo (3DFT-CISS) MRI.

The sensitivity of different MRI sequences in the detection of inner ear malformations in patients presenting with sensorineural hearing loss (SNHL) and/or vertigo was evaluated. We studied 650 patients presenting with SNHL and/or vertigo, clinically not suspected of having inner ear malformations. The sensitivity of T1-weighted, Gd-enhanced T1-weighted and (when available) T2-weighted spin-echo images, and three-dimensional Fourier transformation-constructive interference in steady state (3DFT-CISS) gradient-echo images, to unexpected malformations was assessed. Inner ear malformations were found in 15 (2.3%) of these patients. Enlargement of the endolymphatic duct and sac was the most frequent malformation, found in 11 patients. The 3DFT-CISS images showed all lesions; the other sequences were less sensitive and the pathology was missed, partially or only retrospectively seen in 11 of the 15 patients. Therefore, in addition to the routine unenhanced and Gd-enhanced T1-weighted and T2-weighted images, thin gradient-echo (3DFT-CISS) images are necessary to detect all clinically unexpected inner ear malformations in patients presenting with vertigo and/or SNHL.

Adolescent↗
PubMed2006

[Benign and malignant lesions in the region of the inner ear and cerebellopontine angle].

Tumorous lesions in the region of the inner ear and cerebellopontine angle are very rare and can be classified into benign and malignant disease forms. This contribution presents and explains the CT and MRI characteristics of these tumors.High-resolution computed tomography (HRCT) in the axial projection is applied for evaluation in the high-resolution bone window. The coronary slices can be reconstructed from the axial datasets or in individual cases examined in the coronary plane.HRCT excellently demonstrates osseous lesions and in individual cases - e.g., exostoses - it can simply suffice to perform HRCT of the temporal bone, while HRCT is also excellent for detecting osseous lesions to determine whether the tumor is benign or malignant.MRI, on the other hand, excellently shows the extent of tumor spread because of its superb soft tissue contrast. Consequently, HRCT and MRI images of the inner ear and cerebellopontine angle provide meaningful information for visualization and classification of tumorous lesions. The two methods should not be considered as competing but rather as complementary and among other aspects exert considerable influence on the therapeutic approach.

Cerebellar Neoplasms↗
PubMed2004

No correlation between multilamellar bodies in the inner ear and further organs of mutant (backstroke, bks) and wildtype zebrafish embryos.

The origin of the proteinacious matrix of the inner ear stones (otoliths) of vertebrates has not yet been clarified. Using the backstroke mutant (bks) of the zebrafish Danio rerio, which is characterized by a complete lack of otoliths, we searched for possibly missing or aberrant structural components within the macular epithelia of the inner ears of embryos on the ultrastructural level. Numerous multilamellar bodies (MLBs) were found. The MLBs were, however, not restricted to the inner ears of mutants but were also found in wildtype individuals and in further organs such as brain and liver. MLBs have hitherto never been described from the inner ear of fish and are generally estimated to be rare structures. Their occurrence in fish liver can, however, be induced by using particular chemical substances, which seem to effect adaptive compensatory processes on the cellular level. Such a chemical treatment also affects the ultrastructure of further organelles. Since the occurrence of MLBs in the liver of zebrafish was not accompanied by an alteration of the morphology of other organelles, their occurrence seems not to be due to environmental stress. The findings indicate that the MLBs cannot be correlated with bks-inherent features as well as with missing otolith development/growth. Since the occurrence of MLBs was independent from the developmental stage of a specimen and its overall tissue preservation, it can moreover be excluded that these MLBs merely represent fixation artifacts. Their presence more likely indicates cellular remodelling processes of hitherto unknown significance.

Acoustic Maculae↗
PubMed2000

Identification of synergistic signals initiating inner ear development.

Tissue manipulation experiments in amphibians more than 50 years ago showed that induction of the inner ear requires two signals: a mesodermal signal followed by a neural signal. However, the molecules mediating this process have remained elusive. We present evidence for mesodermal initiation of otic development in higher vertebrates and show that the mesoderm can direct terminal differentiation of the inner ear in rostral ectoderm. Furthermore, we demonstrate the synergistic interactions of the extracellular polypeptide ligands FGF-19 and Wnt-8c as mediators of mesodermal and neural signals, respectively, initiating inner ear development.

Animals↗
PubMed2002

Hair cell development in vivo and in vitro: analysis by using a monoclonal antibody specific to hair cells in the chick inner ear.

The purpose of this study was to establish a hair cell-specific marker and a convenient explant culture system for developing chick otocysts to facilitate in vivo and in vitro studies focusing on hair cell genesis in the inner ear. To achieve this, a hair cell-specific monoclonal antibody, 2A7, was generated by immunizing chick inner ear tissues to a mouse. Through the use of immunofluorescence and immunoelectron microscopy, it was shown that 2A7 immunoreactivity (2A7-IR) was primarily restricted to the apical region of inner ear hair cells, including stereocilia, kinocilia, apical membrane amongst the extending cilia, and superficial layer of the cuticular plate. Although the 2A7 antibody immunolabeled basically all of the hair cells in the posthatch chick inner ear, two different patterns of 2A7-IR were observed; hair cells located in the striolar region of the utricular macula, which consist of two distinct cell types identifiable on the basis of the type of nerve ending, Type I and II hair cells, showed labeling restricted to the basal end of the hair bundles. On the other hand, hair cells in the extrastriolar region, which are exclusively of Type II, showed labeling extending over virtually the entire length of the bundles. These findings raised the possibility that chick vestibular Type II hair cells, characterized by their bouton-type afferent nerve endings, can be divided into two subpopulations. Analysis of developing inner ear by using the 2A7 antibody revealed that this antibody also recognizes newly differentiated immature hair cells. Thus, the 2A7 antibody is able to recognize both immature and mature hair cells in vivo. The developmental potential of embryonic otocysts in vitro was then assessed by using explant cultures as a model. In this study, conventional otocyst explant cultures were modified by placing the tissues on floating polycarbonate filters on culture media, thereby allowing the easy manipulation of explants. In these cultures, 2A7-positive hair cells were differentiated from dividing precursor cells in vitro on the same schedule as in vivo. Furthermore, it was found that hair cells with both types of 2A7-IR were generated in culture as in vivo, indicating that a maturational process of hair cells also occurred. All these results as presented here suggest that the 2A7 monoclonal antibody as a hair cell-specific marker together with the culture system could be a potential tool in analysis of mechanisms underlying hair cell development.

Animals↗
PubMed1987

Scanning electron microscopic observations of the canine inner ear.

The sensory epithelia of the inner ear of the dog have been investigated using scanning electron microscopy (SEM). The surface appearance of the cristae ampullares of the semicircular canals and of the macula utriculi are very similar to other mammalian species. The crista ampullaris of the anterior vertical semicircular canal is divided by a non-sensory septum cruciatum, found in cats and rats but not, for example, in man. The vestibular sensory cells possess two distinct types of stereocilia, one is thick and rigid appearing, the other is thin and limp. Neither type of stereocilium is restricted to a particular hair cell type. From SEM views of the undersurface of the tectorial membrane of the cochlea we show evidence that some inner hair cell stereocilia may be attached to the tectorial membrane. This observation is made only in middle to upper cochlear regions (those subserving transduction of low frequencies of sound).

Animals↗
PubMed2004

Experimental vibratory damage of the inner ear.

The aim of the experiment was to determine the effect of whole-body vibration on the inner ear. The investigations were carried out on 40 guinea pigs, subjected to sinusoidal vibration (10 Hz/5 mm/1.4 g rms) for 1 to 6 months in a noiseless apparatus. Cochlear microphonic measurements were done with a phase-sensitive detection technique for the levels 70, 80 and 90 dB and the frequencies of 0.26, 0.5, 1 and 2 kHz from the apex of the cochlea and for 4 and 8 kHz from the region of the round window. Analysis of 1,440 measurements suggested the possibility of damage appearing in the upper turnings of the cochlea. The subsequent morphological analysis was based on the estimation of the state of the hair cells (a three-degree scale of injury) in a Zeiss DSM 950 scanning microscope and of the structure of the fibers of the acoustic nerve in a Zeiss EM 900 transmission microscope. Vibration-induced changes were seen in all the examined inner ears of the experimental groups. Hair-cell damage was more often seen in the region of the apex, spreading gradually in the direction of the base and from the circumference (outer hair cells of the third row) to the modiolus. The most characteristic vibrational changes of the acoustic nerve fibers occurred in 100% of the examined myelin sheaths and were visible as decreases in their electrodensity. The changes in both the assessed elements of the inner ear appeared simultaneously but independently and were directly connected with the duration of the experiment. The results obtained allow an explanation of the mechanism of hearing loss in persons subjected to whole-body vibration. The damages done to the inner ear structures may cause a worsening of hearing there, especially in the low and medium frequencies.

Animals↗
PubMed1980

Anisocoria in inner ear lesions.

In experiments using rabbits, the pupil on the side of irritative inner ear lesion showed dilatation, and that on the side of paretic lesion showed constriction. In the clinical observation of patients with unilateral inner ear diseases (134 cases), anisocoria was recognized in 54.5%. In 68.5% of these, anisocoria was induced after applying a drop of neosynephrine. The size of the pupil on the healthy side was smaller in 65.8% than the pupil on the healthy side. Anisocoria in inner ear lesions is believed to be due to vestibulo-sympathetic imbalance through the superior cervical sympathetic ganglion.

Adolescent↗
PubMed2005

[Comparing the characteristics of psychophysical tests between cochlear implant children with large vestibular aqueduct syndrome and normal inner ear].

OBJECTIVE: The purpose of this study is to compare the characteristics of psychophysical tests between cochlear implant children with large vestibular aqueduct syndrome and normal inner ear and to analyse the characteristics of psychophysical and impedance tests for cochlear implant patients with large vestibular aqueduct syndrome. METHOD: One hundred and thirty-one cochlear implant pre-lingual deafness patients participated in this study. They received cochlear implant surgery at the age of 1.5 to 12 years old from Nov, 1998 to Aug, 2003. The patients were divided into two groups. Group A had 111 patients with normal inner ear. Group B had 20 patients with radiographically proven large vestibular aqueduct syndrome. All of the patients were inserted with Nucleus 24M. The time of the first programming session was approximately 4 weeks after surgery. The psychophysical tests included T and C-Level tests. The programming techniques used in the test were suitable for the age of the patients. The R116 and R126 software were used to test the impedance of the electrodes automatically. RESULT: Using the independent-samples t-test, the impedance and T/C-Level of each electrode did not differ significantly between group A and B ( P > 0.05). The impedance and T/C-Level were not significantly different between group A and B at the time of switch-on, 1 week, 2 weeks, 3 weeks, 2 months, 3 months, 6 months, 9 months and 1 year after switch-on (P > 0.05). CONCLUSION: The parameters of mapping were not significantly different between cochlear implant children with large vestibular aqueduct syndrome and normal inner ear. The management and procedure of mapping used in cochlear implant children with normal inner ear can be used in the children with large vestibular aqueduct syndrome.

Case-Control Studies↗
PubMed1999

Tectorin mRNA expression is spatially and temporally restricted during mouse inner ear development.

The tectorial and otolithic membranes are extracellular matrices that cover the sensory epithelia of the inner ear. They are required for mechanotransduction and may influence hair-cell development. The mRNA expression patterns for two major glycoproteins of these matrices, alpha- and beta-tectorin, were examined during mouse inner ear development to determine when and where these proteins are produced relative to hair cells and whether tectorin production is continuous or transient. Using in situ hybridisation, alpha- and beta-tectorin mRNAs are first detected in the basal end of the cochlea at embryonic day (E) 12.5, and the distinct patterns observed for each tectorin mRNA in the neonate become visible by E14.5. The neonatal expression patterns indicate that some cell types in the cochlea express both alpha- and beta-tectorin mRNAs, while other cells only express one tectorin mRNA. Although expressed early in development, alpha- and beta-tectorin mRNAs cannot be detected in the cochlea by postnatal day (P) 22. In the saccule and utricle, alpha-tectorin mRNA is detected at E12.5, but beta-tectorin mRNA is not observed until E14.5. Expression of alpha-tectorin mRNA ceases after P15, whereas beta-tectorin mRNA expression continues within the striolar region of the utricle until at least P150. The results show alpha- and beta-tectorin mRNAs are expressed during the early stages of inner ear development, prior to or concomitant with hair-cell differentiation, and before the appearance of hair bundles. The expression patterns suggest different cell types contribute to the formation of the various regions of the tectorial membrane. Although tectorin mRNAs are only expressed transiently during cochlear development, beta-tectorin mRNA is continuously expressed within the striolar region of the utricle.

Animals↗
PubMed1991

Expression of nerve growth factor (NGF) receptors in the developing inner ear of chick and rat.

The expression of nerve growth factor receptors (NGFRs) was studied in the developing inner ear with in situ hybridization in chick embryos and with immunocytochemistry in rat embryos to determine sites of possible functions of NGF or NGF-like molecules in inner ear development. NGFR expression in the chick otocyst and acoustic ganglion is compared with epithelial differentiation and the onset of afferent innervation as determined with fluorescent carbocyanine tracers. In the inner ear of the chick embryo, NGFR mRNA expression shows an alternating pattern in mesenchymal and epithelial tissues. NGFR mRNA is heavily expressed in the mesenchyme surrounding the otocyst (E2-3), ceases at E3-5, and reappears in a thin layer of mesenchymal cells surrounding the membraneous epithelia (E5-13). In the otocyst epithelium, NGFR mRNA expression develops in one anterior and one posterior focus at E3-4.5. NGFR mRNA is expressed in the primordia of the ampullary cristae (E5-7) and possibly the anlage of the utricle; label transiently concentrates in the planum semilunatum of the cristae ampullares and in superior portions of the semicircular canals at E9, but is not seen in differentiating hair cells. In the acoustic ganglion, NGFR mRNA expression begins at E4; at the same time, the first peripheral acoustic nerve processes penetrate the otic epithelium (E4-4.5). The acoustic ganglia remain weakly NGFR mRNA-labeled in the posthatch animal. In the rat embryo, NGFR immunoreactivity is present in the auditory placode at E9, in the periotic mesenchyme at E9-10, and in the medial half of the otocyst at E10-11. At E12, epithelial NGFR expression becomes restricted anteriorly and posteriorly in a pattern similar to that of the chick otocyst and ceases at E13. NGFR immunoreactivity appears transiently in pillar cells of the cochlea in the third week of gestation. NGFR and NGFR mRNA is expressed after E11 in the acoustic ganglia. While NGFR transcripts are expressed in the cochlear ganglion cell bodies, NGFR protein becomes restricted to neuronal processes by the third week of gestation. The vestibular, but not the cochlear (spiral) ganglia remain NGFR-labeled in the adult rat. Onset of NGFR mRNA expression in the acoustic ganglion during the period of afferent fiber ingrowth into the otocyst epithelium is consistent with the hypothesis that NGF-like molecules may have a neurotrophic function for acoustic ganglion cells. Transient expression of NGFRs in secretory cells of the vestibular endorgan and pillar cells in the organ of Corti implicate a role for neurotrophins in the differentiation of these epithelial cell types.

Animals↗
PubMedDate not supplied

Intermediate filament proteins in the embryonic inner ear of mice under normal conditions and after exposure to ototoxic drugs.

The expression of the intermediate filament subclasses cytokeratins (CKs), vimentin, and neurofilament triplet proteins (NFs) was analysed in the embryonic inner ear of the CBA/CBA mouse, in vivo and in vitro, using well-defined monoclonal antibodies. Some of the cultured inner ears were exposed to 1-10 micrograms/ml of the ototoxic drugs gentamicin, ethacrynic acid or cisplatin. There was no difference in the expression of IF pattern in the cultured inner ears as compared with the in vivo developed labyrinths. Exposure to the ototoxic drugs did not affect the expression of CKs, vimentin, or NFs. CKs 8 and 18 were identified in all inner ear epithelia. In the mature hair cells, only the apical surfaces showed immunoreactivity to CKs. In addition, CKs 7 and 19 were visualized in the epithelia involved in maintaining endolymph homeostasis. The ganglion cells showed co-expression of CKs, vimentin and NFs, each having a characteristic localization in the cells.

Animals↗