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At least 19 recordsLinked to original sources
PubMedDate not supplied

Calcium mobilization in isolated epithelial cells of the endolymphatic sac.

Endolymphatic sac epithelial cells were isolated from the endolymphatic sac of the guinea pig by enzymatic and mechanical dissociation. The intracellular free calcium ion concentrations ([Ca2+]i) of the isolated cells were determined using the Ca(2+)-sensitive dye fura-2. The isolated cells were classified into two types, i.e. light and dark cells. In the resting state, [Ca2+]i in the cells was variable in both types of cells. In the presence of 200 microM ATP, there was a rapid rise in [Ca2+]i. These findings suggest that endolymphatic sac epithelial cells may have receptor-mediated Ca channels which may play an important role for a nerve-mediated local feedback system of the endolymphatic sac to regulate homeostasis of endolymph volume, pressure and electrolyte balance.

Animals↗
PubMed1993

Electron microscopical observations of melanin in the endolymphatic sac.

Endolymphatic sacs of pigmented guinea pigs were examined by light and electron microscopy. Melanocytes were located not only in the subepithelial connective tissue but also in the intercellular spaces between the epithelial cells. They projected their dendrites into the epithelium extensively. Melanosomes in several stages of maturation and well-developed Golgi apparatus were seen in the cytoplasm of the melanocytes. Melanosomes were also observed in the membrane-bound vacuoles of the epithelial cells. These findings suggest that melanocytes in the endolymphatic sac are highly capable of producing tyrosinase, synthesizing melanin and transferring melanosomes to the epithelial cells, while melanocytes in the other parts of the inner ear do not show signs of melanogenesis under normal conditions.

Actin Cytoskeleton↗
PubMedDate not supplied

Hypoplasia of the vestibular aqueduct and endolymphatic sac in endolymphatic hydrops.

Four temporal bones from three previously reported cases showing endolymphatic hydrops and pathology of the vestibular aqueduct (VA) and endolymphatic sac (ES) were investigated further. Pathology of the VA and ES was studied by measuring the sizes of the VA and ES, paying particular attention to the proximal rugose portions. A medial-view graphic reconstruction was created to delineate the course and size of the VA, as well as its correlation with neighboring structures (posterior canal and cochlea). In addition, 20 control temporal bones were selected and measured for quantitative study of the sizes of the VA and ES. The four pathologic temporal bones were shown to have small, simple, tube-like VA and ES, without surrounding bony pathology. This appeared to be congenital hypoplasia characterized by hypoplastic funnel-shaped dilatation of the VA and hypoplastic rugose portion of the ES. Anterior dislocation of the distal portion of the VA and poorly developed periaqueductal air cells were also noted in the pathologic bones.

Adolescent↗
PubMed2002

Quantitative anatomy of the guinea pig endolymphatic sac.

The endolymphatic sac is believed to represent one of the primary loci for endolymph volume regulation in the inner ear. Quantitative analysis of physiologic measurements from the endolymphatic sac requires knowledge of the anatomy of the structure, specifically the luminal volume and the variation of cross-sectional area with distance along the sac. Recently techniques have become available to make these measurements. In the present study, fixed, isolated specimens of the guinea pig endolymphatic sac were imaged by high-resolution magnetic resonance microscopy (MRM) or by histological serial sections. Structures were reconstructed and quantified using image analysis software. In specimens imaged by MRM the endolymphatic sac volume, including tissue and lumen, was 359 nl for the intraosseous region and 106 nl for the extraosseous region, totaling 465 nl for the entire structure. The luminal volumes were 131 nl for the intraosseous region and 13 nl for the extraosseous region, totaling 144 nl. In histological specimens the volume, including tissue and lumen, was 414 nl for the intraosseous region and 121 nl for the extraosseous region, totaling 535 nl for the entire structure. The luminal volumes were 152 nl for the intraosseous region and 26 nl for the extraosseous region, totaling 179 nl. Differences in volume estimates obtained by the two methods were not statistically significant and variation was dominated by inter-specimen variation. Pooling the data, the total volume of the endolymphatic sac in the guinea pig including tissue and lumen was 506 nl (S.D. 100, n=17) and the volume of the lumen was 169 nl (S.D. 48, n=14).

Animals↗
PubMed1992

Hyaluronan synthesis in the adult guinea pig endolymphatic sac.

The endolymphatic sac is believed to play a major role in membranous labyrinth homeostasis by controlling the volume of endolymph, removing debris, and participating in the immune response of the inner ear. The endolymphatic sac is postulated to absorb endolymph and to synthesize and secrete high-molecular-weight and osmotically active glycosaminoglycans (GAGs). The present study examines the ability of in vitro adult guinea pig endolymphatic sac cells to synthesize complex proteins and polysaccharides. The intent is to characterize the nature of these compounds by studying carbon-14 (14C) glucose incorporation in tissue cultured endolymphatic sac specimens using autoradiographic and specific enzymatic digestion techniques. Our results suggest that sac cells can synthesize GAGs and proteins in vitro in proportionately larger amounts than surrounding connective tissue and dura. The principal GAG synthesized by the endolymphatic sac appears to be hyaluronan.

Amylases↗
PubMed1979

Lymphocyte-macrophage activity in the endolymphatic sac. An ultrastructural study of the rugose endolymphatic sac in the guinea pig.

The irregular epithelial layer which delimits the intermediate part of the endolymphatic sac, and the surrounding perisaccular tissue, were examined morphologically in the guinea pig by transmission electron microscopy. Specialized areas of the epithelium which have previously been designated as "non-vascularized epithelial processes" (NVP) were constantly observed. These proliferative areas showed a close topographical relation to the free luminal cells and contained an abundance of lymphoid cells. Lymphocytes and macrophages were intimately associated with each other in a manner similar to that seen in these two types of cells in antigen-stimulated lymphoid tissues. There was a marked degeneration and phagocytosis of cells. The richly vascularized perisaccular tissue was rich in plasma cells, monocytes, mast cells and lymphocytes. The latter could be seen to migrate through the endothelial cells in the thin post-capillary venules into the sac tissue. The authors consider that the endolymphatic sac plays a role as an immunological defence organ for the internal ear. A hypothetical model concerning circulation and turnover of certain of the free intraluminal cells in presented.

Animals↗
PubMed1987

Effects of high intensity pure tone stimulation on the endolymphatic sac. Correlations between cochlear morphology and endolymphatic sac response.

A systematic study of the effects of acoustic overstimulation on the endolymphatic sac (ES) in the guinea pig was performed. The ES was studied with light and transmission electron microscopy after exposure of the animals to a 3.85 kHz pure tone of 108 dB SPL or 120 dB SPL for 22.5 min (sound energy 9.4 and 150 Pa2 X h, respectively). The damage pattern in the organ of Corti was studied after various post-exposure times with SEM and correlated with the morphological characteristics of the ES in the same ear. This was made possible by using a modified technique for histological processing. In ears with induced structural abnormalities to the organ of Corti, the ES displayed few morphological changes without obvious signs of accumulation of cell debris within the lumen. Initially an increase in the amount of freely floating cells was found which persisted for at least 24 h. The role of the ES for disposal and digestion of locally produced degeneration products within the cochlea after acoustically generated structural damage is discussed.

Acoustic Stimulation↗
PubMed2001

Morphological and functional characteristics of cells cultured from the endolymphatic sac.

The endolymphatic sac is a part of the homeostasis-regulating system of the membranous labyrinth of the inner ear. Disturbances in the function of the endolymphatic sac are believed to be involved in the genesis of different inner ear disorders, such as endolymphatic hydrops and Ménière's disease. To make studies of the ion- and fluid-regulating mechanisms of the sac possible, a method to culture the tissue in vitro was developed. Epithelial cells and fibroblasts were morphologically characterised in the cell cultures with light and electron microscopy as well as immunohistochemically using antibodies against cytokeratin and vimentin. Since mesenchymal cells have been shown to express vimentin and epithelial cells cytokeratin, the antibodies against these two intermediate filament proteins were used to further confirm the morphological identification. In addition, some functional characteristics of the cultured cells from the endolymphatic sac were studied. ATP and K(+) were added to the cell cultures and changes in cytoplasmic free Ca(2+) concentration ([Ca(2+)](i)) were determined with the fura-2 method. A rapid and transient increase in [Ca(2+)](i) could be seen in both epithelial cells and fibroblasts after applying ATP (200 microM) extracellularly. However, when K(+) was added in concentrations of 50 mM and 100 mM, no changes in [Ca(2+)](i) could be seen in either the epithelial cells or the fibroblasts. The results show that the cultured endolymphatic sac cells preserve their morphological characteristics and maintain a high viability. Accordingly, this method provides a tool for further studies of ion transport mechanisms and fluid homeostasis in the endolymphatic sac.

Animals↗
PubMed1994

Endolymphatic sac enhancement.

Endolymphatic sac enhancement surgery has proved, over the last several decades, to be a conservative and relatively safe procedure for patients in whom extensive empirical medical therapy has failed. The operation can usually be done as an outpatient procedure or with a one-night postoperative stay, and it has relatively low morbidity. Up to 90% of patients exhibit significant improvement of their episodic vertigo after the operation. Destructive procedures such as labyrinthectomy and vestibular neurectomy are reserved for rare cases of failure of the endolymphatic sac enhancement and are not offered to patients as a primary surgical alternative. Wide decompression of the mastoid and sigmoid sinus is of paramount importance in achieving an adequate endolymphatic sac enhancement. At the end of the operation, meticulous attention should be given to cleaning bone dust and debris from the wound and to stopping all bleeding and bony oozing. Wide opening of the posterior aditus and facial recess is usually necessary to prevent postoperative aditus block. In the postoperative period, scrupulous attention should be given to wound healing; if infection develops in the wound, aggressive antibiotic therapy should be administered to prevent labyrinthitis that could result in deafness.

Endolymphatic Sac↗
PubMed1979

The vestibular aqueduct and endolymphatic sac and duct in endolymphatic hydrops.

The histologic features of the endolymphatic sac and duct in 23 serially sectioned temporal bones with idiopathic or secondary endolymphatic hydrops were blindly compared with 22 randomly selected, normal temporal bones. In idiopathic hydrops, the pars rugosa of the endolymphatic sac extended out of the vestibular aqueduct into the dura in 29% of bones, compared with none of normal bones (P less than .01). In the other 71%, the pars rugosa in the vestibular aqueduct was surrounded by dura more commonly than normal. Functional studies are required to assess the relationship of these findings to hydrops. In secondary hydrops (eg, due to labyrinthitis), the endolymphatic duct was obliterated in the isthmus of the vestibular aqueduct by bone or fibrosis in seven of nine bones. Because of similar ossification and fibrosis elsewhere in the vestibular labyrinth, a direct relationship with hydrops cannot be assumed.

Adult↗
PubMed1995

Glycolipidic component of the epithelial cell coat of the endolymphatic sac.

The endolymphatic sac (ES) is thought to synthesize and secrete glycoconjugates such as sulfated glycoproteins into the endolymphatic lumen. Ganglioside Gm1 is a specialized glycolipid containing one sialic acid molecule, which is generally found in the outer leaflet of the cell membrane. This glycolipid, which is known to be a specific receptor for cholera toxin (CT), acts as a membrane transducer and is involved in the modulation of cell metabolism, growth and regeneration. In the present study we identified Gm1 by studying the distribution of the FITC-labeled CT-subunit B in the ES epithelium of adult guinea pigs. Our findings indicate the presence of this ganglioside in the ES, with a predominant localization in the basolateral aspect of the epithelial cell layer. No detectable differences between ES cell types could be identified, whilst the ES distal and intermediate portions showed more reactivity than the proximal portion. This study, which represents the first description of a lipidic glycoconjugate component in the ES, provides evidence in support of the role of the ES in the turnover and regulation of inner ear fluids.

Animals↗
PubMed2001

Mutation of von Hippel-Lindau tumor suppressor gene in a sporadic endolymphatic sac tumor.

Endolymphatic sac tumor (ELST) is a low-grade adenocarcinoma of the temporal bone that is presumed to originate from the endolymphatic system. Although ELSTs are extremely rare in the general population, a significant number of studies have documented the occurrence of ELST among patients with von Hippel-Lindau (VHL) disease. Because of the rarity of the tumor, however, few cases of ELST have been analyzed for mutations of the VHL tumor suppressor gene. In this study, we reported a Japanese male patient with sporadic ELST, along with a molecular genetic analysis of the VHL gene. The light microscopic and immunohistochemical features and clinical presentations were typical of ELST. Sequencing studies of the tumor DNA disclosed a G to T substitution of nucleotide 564, which resulted in an amino acid substitution (Trp to Cys). This is the first report of the VHL gene mutation in a sporadic Japanese case of ELST.

Adenocarcinoma↗
PubMed1992

Experimental interruption of the endolymphatic duct and its effect on the DC potential in the endolymphatic sac.

The endolymphatic sac (ES) of the guinea pig was isolated from the remainder of the inner ear by means of surgical interruption of the endolymphatic duct (ED). The DC potential in the ES lumen and the morphology of the ES were studied using glass micro-electrodes and a light microscope at various time intervals after the interruption of ED. The DC potential did not significantly change 1 h postoperatively, compared to findings in the non-operated ear, but a significant decrease of the DC potential was observed after 1, 3 and 7 days postoperatively. A histologically-stainable substance in the ES lumen was enhanced on the operated side. The isolated ES shows a disturbance of mechanism(s) maintaining the DC potential and there is a secretion of a stainable substance into its lumen.

Animals↗
PubMed2002

Endolymphatic sac tumours.

Endolymphatic sac tumours (ELST) are rare tumours of the petrous temporal bone. They may arise sporadically or be associated with von Hippel-Lindau disease. Their differential diagnosis is discussed. We present the clinical and histopathological features of two new patients with ELST and outline the management of their condition. In addition, we review a third case previously reported as a choroid plexus papilloma in which the histology has been re-assessed and the diagnosis changed to ELST. The controversy regarding the cellular origins of adenomatous tumours of the temporal bone is highlighted.

Adenocarcinoma↗
PubMed2000

Somatic von Hippel-Lindau gene mutations detected in sporadic endolymphatic sac tumors.

Endolymphatic sac tumors (ELSTs) occur sporadically or in association with an autosomal dominantly inherited tumor syndrome, von Hippel-Lindau (VHL) disease. In VHL disease, a germline mutation of the VHL tumor suppressor gene is inherited, and loss of function of the wild-type allele occurs through genetic deletion with subsequent development of neoplastic growth. Genetic alterations associated with sporadic ELSTs are less well understood. In this study, we used tissue microdissection to selectively analyze neoplastic cells from four sporadic ELSTs. In two cases, we detected somatic mutations involving VHL gene exons 1 and 2, respectively. Additionally, one of these cases revealed deletion of the VHL gene locus. Two cases did not reveal VHL gene mutation; one of these two cases showed VHL gene deletion. These results suggest that mutations and allelic deletions of the VHL tumor suppressor gene play a role in the tumorigenesis of sporadic ELSTs.

Adult↗
PubMed2006

Soluble megalin is accumulated in the lumen of the rat endolymphatic sac.

The endolymphatic sac (ES) is believed to play an important role in maintaining homeostasis in the inner ear by the absorption and endocytosis of endolymph. Megalin is a 600-kDa multiligand endocytic receptor expressed in certain types of absorptive epithelia including kidney proximal tubules. We analyzed the immunoreactivity for megalin in rat ES by immunofluorescence, immunogold electron microscopy, and immunoblotting. With immunostaining, the luminal substances of the ES were strongly stained for megalin. Megalin was also localized in luminal macrophage-like cells and both types of epithelial cell (mitochondria-rich cells and ribosome-rich cells). In these cells, the megalin was localized in the lumen of endosomes, but was not membrane associated. This localization pattern indicates that the megalin in these cells is not a membrane receptor, but merely one of the constituents that are endocytosed from the lumen of the ES. Immunoblotting indicated that the megalin in the ES is a 210-kDa molecule lacking a cytoplasmic domain. This suggests that the megalin in the ES may be a soluble form, different from the 600-kDa membrane-bound receptor expressed in kidneys. Taken together, it is likely that the megalin in the ES lumen is a soluble component and may be endocytosed by the ES epithelial cells. Furthermore, we found that the tectorial membrane, an acellular structure in the cochlea, gave a strong megalin immunoreaction. Since the cochlea is connected to the ES, the megalin may be transported alone or with the components of the tectorial membrane from the cochlea to the ES lumen through longitudinal flow.

Animals↗
PubMed1989

The endolymphatic sac and inner ear homeostasis. I: Effect of glycerol on the endolymphatic sac with or without colchicine pretreatment.

The combined effects of glycerol and colchicine on the endolymphatic sac were investigated in mice. Glycerol induced signs of secretion from the epithelium with formation of secretory granules in the light epithelial cells. Other characteristics of the epithelial lining were also changed resulting in an increased widening of the lateral intercellular spaces, a partial collapse of the lumen and with a deposition of a stainable substance within the lumen. This reaction lasted from 30 min to 24 h following the injection. Pretreatment with colchicine was found to decrease or inhibit the glycerol-induced secretion of macromolecules into the sac. The lumen collapsed but frequently there was no presence of stainable substance. Animals treated with both glycerol and colchicine showed marked signs of inner ear malfunction which could indicate that the secretory activity in the sac might be closely related to the regulation of inner ear fluid homeostasis and that functional disturbances in this system may lead to disorders of inner ear function.

Animals↗