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At least 19 recordsLinked to original sources
PubMed1990

Quantitative assessment of the rat stria vascularis.

Stria vascularis tissues from standardized regions in the basal, middle and apical turns of the rat cochlear duct were assessed quantitatively. Strial width, number of marginal cells across the strial width, radial area, as well as the volume density of the different components of the stria vascularis were determined for each standardized region. Strial width, number of marginal cells across the strial width and the radial area were greatest in the basal region and least in the apical region of the cochlea. The volume density of intermediate cells and capillary space was statistically unchanged in the three examined regions of the stria vascularis. However, the volume density of marginal cells and that of basal cells were different between regions. The volume density of marginal cells was highest in the basal turn while the volume density of basal cells was greatest in the apical turn. An objective assessment of the response of the stria vascularis to environmental conditions can be made by kant of its cellular architecture, providing a means to compare the effects of various agents between animal models used to study human inner ear dysfunction.

Animals↗
PubMedDate not supplied

Nongenomic effects of corticosteroids on ion transport by stria vascularis.

Stria vascularis electrogenically secretes potassium into endolymph and this secretion is known to be under acute control of several hormone receptors including purinergic, adrenergic and muscarinic receptors. Recently, chronic application of glucocorticosteroid hormones in autoimmune mice was reported to restore both hearing and normal strial morphology. The purpose of this study was to investigate the acute nongenomic effects of glucocorticoids and mineralocorticoid on the short circuit current (I(sc,probe)) across isolated stria vascularis of gerbils using the voltage-sensitive vibrating probe. Application of prednisolone (0.1-30 microM) caused an increase of I(sc,probe) in a dose-dependent manner with an EC50 of 1.1 +/- 0.2 microM (n = 5). Hydrocortisone (10 microM, n = 5) and dexamethasone (10 microM, n = 5) also increased I(sc,probe), but the response was transient and the response rate was faster than for prednisolone. By contrast, aldosterone (10 microM, n = 6) caused a transient decrease of I(sc,probe )within seconds. These results suggest that prednisolone increased secretion of K+ via a nongenomic mechanism in the range of therapeutic plasma concentrations and that this stimulatory effect of glucocorticoids is specific since the mineralocorticoid aldosterone caused a distinctly different response.

Aldosterone↗
PubMedDate not supplied

Freeze fracturing of the human stria vascularis.

The stria vascularis is an important functional element in the mammalian cochlea. This special tissue is considered to be the source of the endocochlear potential and thus the driving force for the production of a receptor response to the auditory stimulus. In order to maintain its function, the stria vascularis needs to be separated from the endolymphatic space by a tight seal. This seal is comprised of tight junctions in the marginal cell layer. The junctional arrangement in the stria vascularis is described, utilizing the freeze-fracturing technique which allows the visualization of large expansions of plasma membrane. The marginal cells are generally separated by tight junctions of the moderately tight to tight type. In places, however, even so-called leaky junctions with only a few sealing strands are present. Whereas the intermediate cell layer seems to lack tight junctions, the basal cells are connected by extensive tight junctions more or less covering the entire cell. These junctions seem to form an extremely tight barrier against the spiral ligament. Gap junctions are also present in the tissue. Intermediate cells as well as the basal cells are coupled by gap junctions. In the basal cell layer, gap junctional elements may also be found inside the large tight junctions comprising so-called mixed junctions.

Adult↗
PubMed1977

Effect of ethacrynic acid on the stria vascularis.

The stria vascularis of young albino guinea pigs was examined by scanning electron microscopy at intervals of 30, 60, and 240 minutes after the intracardiac administration of ethacrynic acid (70 mg/kg). Results from this study showed that the appearance of large intercellular spaces in the intermediate region of the stria vascularis was due to acute separation of these cells rather than atrophy, as described by previous investigators. It was probable that these spaces were due to an accumulation of extracellular fluid. In some marginal cells, extrusions of cytoplasm into the endolymphatic space were noted in the 240-minute group of animals. The importance of these extrusions is not apparent at this time.

Animals↗
PubMed1991

Primary culture of vital marginal cells from cochlear explants of the stria vascularis.

Explants of the stria vascularis and spiral ligament were dissected from guinea pig cochleae and were successfully cultivated for several weeks. After 2 days, fibroblast-like cells of the spiral ligament covered the bottom of the cell culture dish around the explant. Marginal cells of the stria vascularis proliferated and grew on the luminal surface towards the border of the explant at a rate of 15 microns/day. At day 6 in culture the proliferating marginal cells reached the border of the explant and then advanced to the bottom of the cell-culture dish. There the marginal cells replaced fibroblast-like cells and built an epithelial hexagonal-shaped monolayer. Light microscopic and transmission electron microscopic investigations revealed that the cultured cells were viable and that typical morphological characteristics of marginal cells were preserved. Cultivation of these cells provides a unique model for studies of physiological properties of marginal cells of the stria vascularis.

Acridine Orange↗
PubMed2003

Presbycusis: a human temporal bone study of individuals with flat audiometric patterns of hearing loss using a new method to quantify stria vascularis volume.

OBJECTIVE: The purpose of this study was to determine the prevalence of stria vascularis atrophy in individuals with presbycusis and flat audiometric patterns of hearing loss. Individuals with presbycusis have historically been categorized by the shape of their audiograms, and flat audiometric thresholds have been reported to be associated with atrophy of the stria vascularis. Stria vascularis volume was not measured in these studies. STUDY DESIGN: Retrospective case review. METHODS: Archival human temporal bones from individuals with presbycusis were selected on the basis of strict audiometric criteria for flat audiometric thresholds. Six temporal bones that met these criteria were identified and compared with 10 temporal bones in individuals with normal hearing. A unique quantitative method was developed to measure the stria vascularis volume in these temporal bones. The hair cell and spiral ganglion cell populations also were quantitatively evaluated. RESULTS: Only one of the six individuals with presbycusis and flat audiometric thresholds had significant atrophy of the stria vascularis. This individual with stria vascularis atrophy also had reduced inner hair cell, outer hair cell, and ganglion cell populations. Three of the individuals with presbycusis had spiral ganglion cell loss, three individuals had inner hair cell loss, and all six individuals had outer hair cell loss. CONCLUSIONS: The results of this investigation suggest that individuals with presbycusis and flat audiometric patterns of hearing loss infrequently have stria vascularis atrophy. Outer hair cell loss alone or in combination with inner hair cell or ganglion cell loss may be the cause of flat audiometric thresholds in individuals with presbycusis.

Adult↗
PubMed2005

[Scanning electron microscopic observation of the fetal stria vascularis].

OBJECTIVE: To get full appreciation of the ultrastructural features in the stria vascularis of human fetal cochlea. METHOD: The Stria vascularis in human fetal cochlea were observed by scanning electron microscope. RESULT: The cells of the fetal stria vascularis present round. All cell surfaces are covered with a thick layer of microvilli. The transition zone is between the stria vascularis and the spiral prominence. The shape of cells gradually changes on the spiral prominence and becomes more irregular. Several cells have a structure of elongated hexagons. The structure of the intermediate cells, basal cells and capillary were also observed from the fractural surface in the stria vascularis. CONCLUSION: The surface structures of the whole stria vascularis were observed by scanning electron microscope, especially the surface appearance of the marginal cells. New information will be provided for understanding the structure and function in the stria vascularis.

Cochlea↗
PubMed1999

Immunological identification of an inward rectifier K+ channel (Kir4.1) in the intermediate cell (melanocyte) of the cochlear stria vascularis of gerbils and rats.

The cochlear stria vascularis produces the positive endocochlear potential (EP) and the endolymph. Both the EP and the endolymph are essential for the physiological function of hair cells. The intermediate cell is one of several cell types constituting the stria vascularis. It is known that inward rectifier K+ channels can play a constitutive role in the determination of the resting membrane potential. Localization of a member of the inward rectifier K+ channel family, Kir4.1, in the stria vascularis of gerbils and rats was investigated by immunological methods. A polyclonal antibody specific to the C-terminus of the rat Kir4.1 channel was raised in rabbits. Immunostaining of dissociated cells revealed that the Kir4.1 channel was localized to the intermediate cell, but not to the epithelial marginal cell. Subcellular localization of the Kir4.1 channel to the plasma membrane of the intermediate cell was confirmed by immunoelectron microscopy. Immunostaining of whole-tissue preparations revealed a network-like structure composed of intermediate cells. It seems likely that the Kir4.1 channel mediates the inwardly rectifying K+ current in the intermediate cell as shown previously by electrophysiological methods, and that this channel plays key roles in the production of the EP and K+ transport in the stria vascularis.

Amino Acid Sequence↗
PubMed1992

[Marginal cells of the stria vascularis in vitro].

Explants of stria vascularis and spiral ligament of the guinea pig cochlea were cultivated and after 2 days fibroblast-like cells were found growing around the explant. Marginal cells advanced at 15 microns/day to the border of the explant, and after 2 weeks they proliferated on top of a thin layer of fibroblast-like cells outside the explant, replacing several layers of fibroblast-like cells. Tight junctions and interdigitations of the lateral membranes were found between all neighbouring marginal cells. Their apical surface was covered by microvillus-like membrane extensions. The basal membrane of the new marginal cells did not interdigitate with the underlying membranes of fibroblast-like cells; there was always a gap between the two cell types. The results demonstrate that marginal cells of the stria vascularis are capable of repairing damage to the epithelium, such as may be caused by endolymphatic hydrops, even if the luminal side contains perilymph-like fluid. Furthermore, the cell culture allows living, clearly identified marginal cells to be studied in vivo.

Animals↗
PubMed2003

Aquaporin-1 (AQP1) is expressed in the stria vascularis of rat cochlea.

Cochlea endolymph, produced by the stria vascularis, is essential for normal inner ear function. Abnormal endolymphatic volumes correlate closely with pathological conditions such as Ménière's disease. The critical roles played by aquaporins, which facilitate osmotic movement of water molecules, are known in a variety of tissues. We investigated the expression of aquaporin-1 (AQP1) in the rat inner ear using reverse transcription polymerase chain reaction and immunohistochemical methods. We obtained novel data showing that not just AQP1 mRNA but also AQP1 protein is expressed in the stria vascularis, in addition to other data confirming previous reports. AQP1 immunoreactivity localized to the intermediate cells in the stria vascularis. The above finding suggests that AQP1 may play a role in the water distribution associated with vigorous ion transport in the stria vascularis since the intermediate part of the stria vascularis contains both intermediate cells and the basolateral parts of marginal cells, both of which express ion transporters abundantly.

Animals↗
PubMed1994

Reserpine inhibits the NaK ATPase activity of the stria vascularis in the cochlea.

The function of the stria vascularis in the cochlea is believed to be the production of endolymph. The mechanisms that maintain or control the function of the stria vascularis, however, remain unclear. In the present study, the effects of one-shot reserpine administration on the NaK ATPase activity of the stria vascularis in guinea pigs were investigated. NaK ATPase activity was shown to be completely inhibited 3 to 20 days after reserpinization, and was detectable again 60 days after reserpinization. As reserpine is an adrenergic neuron blocker, these results suggest that catecholamines may play an essential role in the maintenance or control of NaK ATPase activity, and that the stria vascularis may be one of the target organs of catecholamines.

4-Nitrophenylphosphatase↗
PubMed1999

Differentiation of cyst-forming stria vascularis tissues in vitro.

The marginal cells of the stria vascularis possess distinctive morphological characteristics associated with their role in endolymph production. Interestingly, when stria-derived epithelial cells are grown in association with the underlying mesenchyme, the final differentiation of these cell types does not occur. Beyond the rudimentary polarity that is established, similar to that shown in epithelial monolayers, cells in culture bear only a slight resemblance to their marginal cell counterparts in vivo. The ultrastructural features that typify these epithelia, extensive cytoplasmic invaginations, with an abundance of mitochondria, and darkly stained cytoplasm, are not evident under standard culture conditions. In order to determine whether fluid transport, a key function of the stria vascularis, has an effect on the ultrastructural morphology, we examined de novo stria vascularis tissues that formed a fluid-filled cyst in vitro. We found that only cells associated with the luminal structure demonstrated dark cytoplasmic staining and amplification of the basolateral membrane of the marginal cells. Additionally, other epithelial features, such as mitochondria-rich and microvilli-rich cells, were observed in cyst-forming tissues. The enhancement of the marginal cell specializations was not as robust as that observed in vivo; however, they were clearly more extensive when compared to cells in the same culture that were not associated with a fluid-filled lumen. Thus it appears that fluid transport may be necessary to maximize differentiation of stria vascularis tissues in vitro.

Animals↗
PubMed2004

Mechanisms of apoptosis induced by cisplatin in marginal cells in mouse stria vascularis.

Degeneration of the stria vascularis (SV) is amongst the major causes of cisplatin (CDDP)-induced hearing impairment. The pathways of apoptosis occurring in the SV due to CDDP were examined using a mouse experimental model. Temporal bones of adult C57BL/6 mice were collected on days 3, 7 and 14 after the local application of CDDP. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay and immunostaining for apoptosis-related proteins or reactive radical species were employed for analysis. Local application of CDDP caused apoptotic cell death of marginal cells 3 days after CDDP treatment. Immunohistochemical analyses demonstrated activation of caspase-3 and -9, but not -8, and redistribution of cytochrome c in affected marginal cells, indicating a caspase-dependent, mitochondrion-mediated apoptotic pathway in marginal cells. Temporary expression of hydroxynonenal, nitrotyrosine and inducible nitric oxide synthase in the SV was observed at the induction of apoptosis in marginal cells. CDDP toxicity generates reactive radical species in the SV, which causes mitochondrial membrane permeabilization leading to apoptosis of marginal cells.

Aldehydes↗
PubMed1995

Dopamine inhibits the Na-K ATPase activity of the stria vascularis in the cochlea. In vivo ultracytochemical study.

It is believed that the function of the stria vascularis in the cochlea is to produce endolymph. However, the mechanisms that maintain and control the function of the stria vascularis remain unclear. In the present study, to clarify the role of humoral substances in the stria vascularis, a cerium-based method was used to investigate the ultracytochemical effects of intraperitoneal dopamine administration on ouabain-sensitive, K(+)-dependent, p-nitrophenylphosphatase (K-NPPase) activity, which is the second step in the formation of the Na-K ATPase complex, in the stria vascularis of guinea pigs. Na-K ATPase activity was shown to be completely inhibited after dopamine administration. This observation suggests that dopamine inhibits Na-K ATPase activity in the marginal cells of the stria vascularis, and that the stria vascularis may have dopamine receptors. Catecholamines may play an important role in the maintenance and/or control of stria vascularis function.

Adenosine Triphosphatases↗
PubMed2004

Spiral ligament and stria vascularis changes in cochlear otosclerosis: effect on hearing level.

OBJECTIVE: To investigate the effect of changes within the spiral ligament and stria vascularis on hearing in cochlear otosclerosis, we examined spiral ligament hyalinization, stria vascularis atrophy, and sensory hearing loss in cochlear otosclerosis and described changes in ion transport molecule expression. STUDY DESIGN: Retrospective. SETTING: Tertiary referral center. PATIENTS: Thirty-two cochleae from 24 temporal bone donors with histologic evidence of cochlear otosclerosis, including spiral ligament hyalinization. INTERVENTION: Audiography. MAIN OUTCOME MEASURES: Measurements of spiral ligament width, stria vascularis, and bone-conduction thresholds were compared by the amount of hyalinization. Expression of the ion transport molecules Na,K-ATPase, connexin 26, and carbonic anhydrase II were assessed by immunohistochemical techniques. RESULTS: Hyalinization most often involved the posterior basal turn (88%) and the posterior middle turn (27%). Spiral ligament hyalinization correlated significantly with stria vascularis atrophy in the posterior middle turn of the cochlea (rho = -0.63, p < 0.01). There was a trend toward a significant association in the posterior basal turn (rho = -0.31, p < 0.08). Bone-conduction thresholds at 2,000 and 4,000 Hz were significantly associated with the amount of stria vascularis atrophy (rho = -0.44, -0.40, p < 0.05). In addition, we observed decreased immunostaining for both carbonic anhydrase II with Type I fibrocytes and Na,K-ATPase with stria vascularis and Type II and Type IV fibrocytes of the spiral ligament in cochlear otosclerosis sections compared with normal cochlea. Na,K-ATPase staining within the stria vascularis was further decreased in the presence of spiral ligament hyalinization. No significant differences were seen with connexin 26 immunostaining. However, immunostaining results were somewhat inconsistent. CONCLUSION: These data suggest that spiral ligament structure and function are essential for stria vascularis survival. In addition, dampened expression of ion transport molecules within the spiral ligament and stria vascularis may disrupt potassium ion recycling, resulting in loss of endocochlear potential and sensory hearing loss.

Aged↗
PubMed1984

Ultrastructural study of the effect of acute hyper- and hypotension on the stria vascularis and spiral ligament.

The effects of acute hyper- and hypotension on the stria vascularis and spiral ligament of the rat were studied electron microscopically with the horseradish peroxidase (HRP) tracer method. Acute hypertension was induced by i.v. infusion of methoxamine chloride (Mexan), and acute hypotension by i.v. infusion of a ganglion-blocker (Arfonad) and by venesection. In both acute hyper- and hypotensive experiments, a large amount of leaked HRP spread into the intercellular spaces until it was stopped by tight junctions bordering the stria vascularis. The stria capillary endothelium displayed a dense distribution of labelled vesicles, which suggests increased vesicular transport. There was no extravasation of HRP from capillaries in the spiral ligament, despite the presence of some labelled pinocytotic vesicles. The present paper deals with the discovery of enhanced capillary permeability of the stria vascularis under acute hyper- and hypotension, and makes comparison between acute hyper- and hypotension in order to define the function of the stria vascularis.

Animals↗
PubMed1988

Tissue oxygen tension in the stria vascularis.

Tissue oxygen tension in the stria vascularis was successfully measured in cats using the polarographic technique. A correlation study using the differential coefficient between oxygen tension in the stria vascularis and systemic blood pressure proved that vascular autoregulation is present in the mean systemic blood pressure range between 40 and 80 mmHg. The anatomical findings and the response patterns to different gas inhalations indicated that the type of vascular regulation present is more closely related to chemical control than to auto-regulation.

Animals↗