PubMed Health⌕ Search

Biomedical subjects

H Rask-Andersen

Publications and source records attributed to H Rask-Andersen.

At least 37 records · Page 2Linked to original sources
PubMed1989

Lectin detection of carbohydrates in the endolymphatic sac.

The carbohydrate contents of the guinea pig endolymphatic sac were investigated by the use of lectins. The lumen of the endolymphatic sac was filled with stainable precipitate containing N-acetyl glucosamine, mannose, glucose, galactose and fucose. N-Acetyl galactosamine was also detected but in minute amounts. This composition corresponded to other areas in the inner ear, such as the cupula, the otolithic membrane and the tectorial membrane. The function of these carbohydrates may play an important role in preventing the lumen of the endolymphatic sac from collapsing as well as in regulating transepithelial fluid transport.

Acetylgalactosamine↗
PubMed1989

Epithelial cell surface morphology in the endolymphatic sac: a scanning electron microscopic study in the mouse.

The apical, lateral and basal surface structures of the epithelial cells in the murine endolymphatic sac were studied using the freeze-cracking technique and scanning electron microscopy. In this way, it was possible to visualize the luminal surface and the interior of the cell simultaneously. The light epithelial cells, with their smooth rounded nuclei and many mitochondria, had numerous microvilli on their apical cell surface, whereas the dark epithelial cells, with indented nuclei, had only a few such microvilli. The lateral surfaces of these cells were flat, with few projections facing a dilated lateral intercellular space.

Animals↗
PubMed1989

Does severe water deprivation affect the inner ear? An experimental study of the gerbilline endolymphatic sac.

Through an ultrastructural study of the endolymphatic duct (ED) and sac (ES) system, the effects of an impaired body fluid metabolism on the inner ear fluid environment in the mongolian gerbil has been evaluated. A dehydrative state has been determined depriving of water for both five and twelve days this desert animal, which is known to withstand long periods of water abstinence. The morphological changes of the ED and ES under these circumstances have been compared with those induced by ethacrynic acid intoxication. Although the cochlear partition did not show signs of damage, the ED and ES system seems to be negatively influenced by the dehydrative state and displays a marked imbibition of the subepithelial tissue, which at places shows accumulation of an organic matrix. A regulating role for the antidiuretic hormone on the inner ear fluids of the mongolian gerbil is also proposed and discussed.

Animals↗
PubMed1989

Turnover of sulphur compounds in the endolymphatic sac: an autoradiographic study in the Mongolian gerbil.

Complex macromolecules are suggested to play an important role for the function of the endolymphatic sac (ES). As proposed in previous experimental studies, proteoglycans are supposed to be present in the ES. As they are composed of a proteic core linked to chains of glycosaminoglycans, chemical identification of the glycosaminoglycans is of particular importance, bearing in mind that all but hyaluronic acid contain sulphur. In order to follow the short-term turnover of sulphur in the ES, an autoradiographic study has been carried out in the Mongolian gerbil using 35S as tracer. Radioactive labelling of the gerbilline ES was controlled 15, 20, 30 and 60 min after intraperitoneal injection. While the first signs of the presence of radioactive sulphur were noticed after 20 min in the blood vessels and in the basal aspect of the ES epithelium, after 60 min it was possible to observe the presence of the tracer both within the epithelial cell layer as well as in the lumen of the ES. These findings are consistent with the presence of a fast turnover of sulphur molecules in the gerbilline ES.

Animals↗
PubMed1989

Effect of acetazolamide (Diamox) on the endolymphatic sac.

The effect of acetazolamide on the ultrastructures of the murine endolymphatic sac was investigated. The animals were given a single intravenous dose of acetazolamide (100 mg/b.w.) and were sacrificed 0, 15, 30, 60 and 120 min after the injection, respectively. Prominent changes in the fine structure of the epithelial cells could be observed after 30 min. These alterations were even more pronounced after 1 h. After 2 h, the normal cell structure became to be reestablished. The most conspicuous change was a general reduction in the electron density of the dark cells. This was accompanied with a decreased number of cell organelles, especially ribosomes. Some light cells also underwent temporal modifications in their structure in the form of a reduced nuclear stainability associated with a loss of pinocytotic vesicles near the apical plasmalemma. In general, the dark cells seemed to be more influenced by acetazolamide than the light cells. The possibility that the dark cell changes are related to a modification of transepithelial ion and water flow is discussed.

Acetazolamide↗
PubMed1989

Effects of hyperosmolar substances on the endolymphatic sac.

The murine endolymphatic sac (ES) was studied 15 min to 8 hours after intravenous glycerol administration. Initially the ES showed varying degrees of obliteration and this was mostly pronounced at 15-60 min after the injection. After 2 hours the normal volume was regained and after 4 hours the lumen was dilated to 160% of its normal volume. After 6-8 hours the ES had almost regained its normal appearance. The epithelial lining showed an increase in the number of granular cells which, after two hours, reached a peak of 15.8% (p less than 0.01) compared to normal controls which showed 6.1% granular cells of total cell population in the ES. The increase of granular cells was accompanied by filling of the ES lumen with a stainable substance. The epithelial reaction may serve the purpose of counteracting decreases in endolymph pressure either in the ES or in the entire labyrinth.

Animals↗
PubMed1989

The effects of glycerol on vestibular function and the endolymphatic sac after pre-treatment with colchicine.

The endolymphatic sac (ES) is believed to absorb endolymph. Recent studies have suggested that the ES also has a secretory capacity, a function that may be related to the regulation of inner ear fluid volume and pressure. Other studies indicate that hyperosmolar substances, such as glycerol and urea, may initiate a secretion of glycoprotein into the ES. This function was suggested to be related to a regulatory function of the ES by which it can compensate for a decrease in endolymph pressure. In order to investigate this regulatory potential of the ES, the effect of glycerol on the ES was investigated with or without the presence of pharmacological inhibition of glycoprotein secretion through colchicine treatment. Animals treated in such a way showed marked signs of impaired inner ear function, including loss of postural control and loss of Preyer's reflex. Significant ultrastructural changes were noted in the endolymphatic sac suggesting a disturbed secretory activity. The results may indicate that the endolymphatic sac may actively respond to changes in endolymph homeostasis through secretion of macromolecular substances and that alterations in this secretion may lead to functional disturbances of the inner ear.

Animals↗
PubMed1988

Subcellular changes in the endolymphatic sac after administration of hyperosmolar substances.

The effects of hyperosmolar substances on the ultrastructure of the endolymphatic sac were studied in mice. Fifteen minutes after intravenous injection of urea or glycerol, subcellular changes in the endolymphatic sac were observed. These consisted of the occurrence of abundant cytoplasmic granules with a floccular or lamellar material, or both, in the light epithelial cells. Similar material was also present in the lumen of the endolymphatic sac, suggesting a common source and increased secretory activity. Mannitol caused similar changes, though less pronounced. The possibility that the alterations in the fine structure of the endolymphatic sac may be associated with a reduction in the hydrostatic fluid pressure in the rest of the labyrinth is discussed.

Animals↗
PubMed1988

Variations in surgical anatomy of the endolymphatic sac.

Twenty-nine specimens of the extraosseous portion of the human endolymphatic sac (ES) were serially sectioned longitudinally. The length and width of the extraosseous ES were measured and the surface area was calculated. As the specimens included the sigmoid sinus (SS), the relationship between the ES and the SS was analyzed. The extraosseous ES varied considerably in size. The lumen either consisted of a single tube or was subdivided into several tubules. The distal part of the ES overlapped the SS in one third of the specimens. The results indicate that a minute extraosseous ES could explain the sometimes difficult task of localizing this structure at ES surgery. The great variability in size might perhaps also explain the varying results of this surgery.

Adult↗
PubMed1988

Immunohistochemical localization of Na+, K+-ATPase in the human endolymphatic sac.

The presence and distribution of the transport protein complex Na+,K+-ATPase in the human endolymphatic sac (ES) was demonstrated immunohistochemically using a monoclonal antibody directed toward the denatured catalytic subunit of Na+,K+-ATPase from lamb kidney medulla. Our findings support an active transcellular ion exchange by the ES epithelium with subsequent passive transcellular and paracellular outflow of water. The possible role of the lateral intercellular spaces in the outflow of endolymph at the level of the ES is discussed.

Antibodies, Monoclonal↗
PubMed1988

The basement membrane and associated structures in the murine endolymphatic sac.

The ultrastructure of the basement membrane of the murine endolymphatic sac was studied under various experimental conditions in labyrinthectomized and ethacrynic acid-treated animals and was compared with normal anatomy. The basement membrane was clearly visualized after staining with ruthenium red or dialyzed iron. The basement membrane of the murine sac consists of two different layers: the lamina rara and the lamina densa. It demarcates the border between the epithelial cells and the subepithelial connective tissue. Our findings suggest that the basement membrane acts as a physical support to the epithelium in the endolymphatic sac. The basement membrane also shows a dynamic capacity to form a new basement membrane, with the result that the lateral intercellular space between contiguous epithelial cells may be integrated with the subepithelial space. This system is believed to act as a macromolecular and bulk water transport system. In the subepithelial space, collagen, reticular and elastic fibrils are found having a close relationship to the basement membrane. The elastic fibres are presumed to play a role in the pressure-regulating mechanism in the endolymphatic sac.

Animals↗
PubMed1988

The surface morphology of the endolymphatic sac of the Mongolian gerbil (Meriones unguiculatus) (a scanning electron microscopic study).

A scanning electron microscopic study of the endolymphatic sac of the mongolian gerbil is presented. As described in other animal species and in man, three rather distinct regions on the epithelial surface can also be recognized in this rodent. Light and dark cells are seen to line the sac epithelium throughout. At the level of the intermediate portion, however, a different cell type--the granular cell--is present, with its luminal surface covered by large amounts of solid material. On the basis of light and transmission electron microscopic studies presented elsewhere, a higher degree of functional specialization in this portion of the gerbilline sac is proposed.

Animals↗
PubMed1988

Ruthenium red staining of the endolymphatic sac in the guinea pig.

The ultrastructure of the guinea pig endolymphatic sac was studied, using the ruthenium red staining technique. The dye stained the apical cell surface coat and the homogeneous substance in the luminal space of the endolymphatic sac, when introduced from the luminal side of the epithelium. It is suggested that the surface coat and homogeneous substance may play an important part in the endolymph regulatory mechanism in the endolymphatic sac. When ruthenium red was introduced from the subepithelial side, the basolateral surface of the epithelial cells usually became brightly stained in the absence of staining of the apical cell surface, due to the presence of the tight junctions. In some instances, however, the dye penetrated beyond the level of the tight junctions. Pinocytotic vesicles and larger vacuoles in the epithelial cells were also sometimes stained, both apically and near the lateral cell surface. These findings suggest that endolymph efflux mechanisms in the endolymphatic sac may involve the combined actions of a paracellular and transepithelial flow as well as a transcellular, vacuolar bulk flow.

Animals↗
PubMed1988

Effects of ototoxic diuretics (loop diuretics) on the endolymphatic sac.

The acute and chronic effects of treatment with ethacrynic acid (EA) and furosemide (FU) on the structure of the murine endolymphatic sac were studied by means of light and transmission electron microscopy. The animals were treated with loop diuretics in doses which are known to cause morphological alterations of the stria vascularis and a significant reduction of the endocochlear potential. A single intravenous injection of either EA or FU resulted in immediate morphological changes such as an increase in cytoplasmic contents of endoplasmic reticulum and more prominent Golgi structures of the light cells. These cells developed membrane-bound granules and a smooth tubular network in the apical cytoplasm. These findings together with the appearance of a precipitate on the luminal aspect of the cell membrane suggested secretory activity. Ten days after daily intraperitoneal injections with loop diuretics in subtoxic doses, the epithelial cytoarchitecture of the endolymphatic sac was altered, with pronounced veiling of the light cells by the dark cells. It is concluded that the changes in the endolymphatic sac epithelium after treatment with ototoxic diuretics may not be a result of a primary toxic effect on the sac per se, but rather be secondary to alterations in fluid and ion homeostasis in the rest of the inner ear.

Animals↗
PubMed1988

Ultrastructural localization of carbonic anhydrase and its possible role in the endolymphatic sac.

Carbonic anhydrase was detected histochemically in the guinea pig endolymphatic sac. The enzyme reaction was positive in both light and dark epithelial cells. In the former, the reaction product was found in the cytoplasm, especially around the intracytoplasmic vesicles and vacuoles. Reaction product was found in the basolateral infoldings as well. The dark epithelial cells also displayed carbonic anhydrase activity in the cytoplasm as well as in the lysosome-like bodies. It is suggested that this enzyme may be involved in (1) ionic or fluid regulation of the endolymph, (2) otoconia metabolism, and (3) phagocytotic activities.

Animals↗
PubMed1987

Three-dimensional ultrastructure of the endolymphatic sac.

The subcellular structures of the epithelial cells of the guinea pig endolymphatic sac were studied. By using a newly developed scanning electron microscopy technique, the intracellular organelles could be studied three-dimensionally and the topographic relationships analyzed. The light epithelial cell has an extensive network of endoplasmic reticulum which is characteristically arranged in a baso-apical direction. The connections between the inner surface of the plasmalemma and the endoplasmic reticulum were observed, as were connections between the Golgi complex and the endoplasmic reticulum. Our findings support the hypothesis that the endoplasmic reticulum might form transcellular channels through which the cell can transport water and ions from the lumen of the endolymphatic sac out into the subepithelial tissue. The dark epithelial cells seen in particular contained the smooth type of endoplasmic reticulum. Lysosomes were also observed in the dark cells, indicating that these cells probably have more of a secretory function.

Animals↗
PubMed1987

Ultrastructure of the endolymphatic sac in the mongolian gerbil.

We describe our findings in an ultrastructural study of the endolymphatic sac of the mongolian gerbil. In conjunction with its specific renal physiology, enabling this animal to withstand long-term water deprivation, we have used our findings to hypothesize the existence of a local monitoring system within the endolymphatic space. The presence of elastic tissue in the subepithelial space of the endolymphatic sac could explain the mechanism through which this structure equilibrates endolymphatic pressure changes. Finally, we propose that a secretion of water-retaining macromolecules may act through osmotic forces to modulate inner ear fluid.

Animals↗