Biomedical subjects

H Rask-Andersen

Publications and source records attributed to H Rask-Andersen.

At least 55 records · Page 3Linked to original sources

PubMed1991

Three-dimensional analysis of 61 human endolymphatic ducts and sacs in ears with and without Menière's disease.

We used light microscopy and computerized graphic reconstruction techniques to examine the endolymphatic duct and sac in 20 pairs of bones from patients with Menière's disease and 21 bones from controls. The diameters of the endolymphatic duct and the proximal portion of the vestibular aqueduct were significantly smaller in Menière's disease ears than in controls. Graphic reconstructions showed the Menière's sacs to be smaller and to have fewer tubular epithelial structures in the intraosseous portion than in the control ears. The median volume of the sac in the Menière's disease side was substantially lower than in the contralateral ear. The width of the external aperture of the vestibular aqueduct was significantly smaller in Menière's disease ears than in controls. These findings indicate that the size not only of the vestibular aqueduct but also of the sac is reduced in Menière's disease. The results may suggest that the endolymphatic sac is pathologically changed in Menière's disease and that a reduced resorptive capacity of a small endolymphatic sac could result in endolymphatic hydrops.

Aged↗

PubMed1991

Lymphocyte-macrophage activity in the human endolymphatic sac.

The human endolymphatic sac was analysed electron microscopically in patients undergoing acoustic Schwannoma surgery or vestibular nerve section. In addition, endolymphatic sacs from cadavers were analysed light microscopically. The results show that the human sac is endowed with a variable number of leucocytes and that there is a continuous recirculation of immuno-competent cells in this area of the inner ear that may be of importance for clearance of the inner ear from foreign substances and microorganisms derived from nearby located infection-prone areas. The possibility in Meniere's disease of a disturbed immunological activity in the sac is discussed.

Ear, Inner↗

PubMed1991

Modulation of the endolymphatic sac function.

A method for inducing a partial dysfunction of the endolymphatic sac and its effect was investigated. Acetazolamide as well as amiloride caused collapse of the lateral intercellular spaces in the endolymphatic sac epithelium and a subsequent mild endolymphatic hydrops. These changes indicate a decreased absorption rate of endolymph in the endolymphatic sac. Colchicine caused a disturbed secretory activity of the sac induced by glycerol. Animals treated with colchicine showed marked signs of inner ear malfunction after additional treatment with glycerol, which might indicate that the secretory activity in the sac is closely related to the regulation of inner ear fluid homeostasis and functional disturbance.

Acetazolamide↗

PubMed1990

Three-dimensional anatomy of the human endolymphatic sac.

Computerized and graphic three-dimensional reconstruction of a human endolymphatic duct and sac (ES) showed the ES to be a fusiform and flattened structure with marked tubularity, especially in the extraosseous region. The specimen was 18.2 mm long. It measured 60 X 200 microns at the isthmus portion of the endolymphatic duct and 200 X 7000 microns at the broadest part of the ES. The volume of the endolymphatic duct was 0.03 mm3 and of the ES, 1.85 mm3. The extraosseous ES volume represented more than two thirds of the total ES volume.

Computer Graphics↗

PubMed1990

High-resolution scanning electron microscopy of the murine olfactory receptor.

The anatomy of the murine olfactory receptor was analyzed using high-resolution scanning electron microscopy with the aldehyde-osmium-dimethyl sulfoxide-osmium method. A good three-dimensional image of the receptor cell architecture was obtained. Within the olfactory vesicle, a complex tubular network was found that seemed to be physically associated with adjacent organelles, the basal aspect of cilia, and the lateral plasmalemma. It is assumed that these structures may be of significance during the olfactory transduction process.

Animals↗

PubMed1990

A technique for reembedding celloidin sections for electron microscopy.

A new technique for reembedding celloidin sections of human temporal bones for transmission electron microscopy is described. It consists of four steps: 1. loosening of celloidin sections from glass slides with use of xylene and dissection of the area of interest, 2. removal of celloidin with use of clove oil, 3. staining with 1% osmium tetroxide and 1% tannic acid, and 4. embedding in epoxy resin. Autolytic changes were seen due to poor fixation. TEM of reembedded celloidin sections of optimally fixed tissue revealed that the celloidin-embedding procedure affected ultrastructural preservation to some degree. This included less well-preserved cell membranes and some increased electron density of the cytosol decreasing the EM resolution of intracytoplasmic organelles. The technique allows TEM analysis of the intact labyrinth at all regions in the same specimen without dissection of the fragile tissue components of the membranous labyrinth. This might make the technique useful for processing freshly fixed human inner ear tissue and temporal bones for ultrastructural histopathological analysis.

Animals↗

PubMed1990

Size variations in the lateral intercellular spaces of the endolymphatic sac induced by dietary factors.

Since much evidence suggests that the endolymphatic sac is responsible for endolymph resorption, and that the endolymphatic sac lateral intercellular spaces which are lined by the energy-dependent transport complex NA+,K(+)-ATPase are important in this process, we sought to evaluate the effects of dietary salt and a food extract that inhibits the activity of Na+,K(+)-ATPase on lateral intercellular space size. Animals fed this food factor and a high-sodium diet had significantly smaller endolymphatic sac lateral intercellular spaces than those animals fed only a high-sodium diet (analysis of variance with Scheffe's multiple comparison test, P less than 0.001). Animals fed a high-sodium diet had significantly larger endolymphatic sac lateral intercellular spaces than those animals fed a control diet only (analysis of variance with Scheffe's multiple comparison test, P less than 0.001). Results of this study suggest that dietary sodium affects endolymphatic sac fluid dynamics and that other food factors may regulate sodium metabolism, and therefore endolymphatic sac function.

Animals↗

PubMed1990

Transmission electron microscopy of previously embedded celloidin sections.

A technique to re-embed celloidin sections of human temporal bones for transmission electron microscopy (TEM) is presented. The procedure consists of basically four different steps, starting with loosening of the celloidin sections from the glass slides, removing the celloidin using clove oil, to staining and embedding in epoxy resin. The technique allows TEM analysis of the intact labyrinth in various regions in the same specimen, as well as on the same section. This may prove useful, as prior dissection of the fragile tissue components of the membranous labyrinth is not longer necessary. The technique makes possible the retrospective study of temporal bone collections. It may also be of value for the study of the ultrastructural histopathology of the human inner ear in optimally preserved tissue.

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↗

PubMed1989

The endolymphatic sac and inner ear homeostasis. II: Effect of glycerol on the sensory end organs with or without colchicine pretreatment.

The effects of glycerol and colchicine on the sensory end organs of the inner ear were investigated in mice. Glycerol alone induced a widening of the intercellular spaces lining vestibular dark and transitional cells as well as the marginal cells of the stria vascularis. This was noted within 30 min after the injection of glycerol and was normalized again within 4 h after the injection. Colchicine induced some morphological changes in the inner ear sensory cells, such as dissociation of Golgi complexes etc. These isolated glycerol or colchicine injections did not cause any signs of inner ear functional impairment. Treatment with glycerol following pretreatment with colchicine, however, induced marked inner ear dysfunction with impaired sense of balance and audition. The inner ear morphology revealed a combination of changes as compared with what was observed after isolated treatment with glycerol or colchicine i.e. edema of the stria vascularis, and vestibular dark and transitional cells as well as dissociation of Golgi complexes in the sensory cells. The cochlea showed moderate endolymphatic hydrops. These findings indicate that colchicine affects the inner ear fluid regulating mechanisms which may lead to severe functional derangement after additional glycerol treatment. It is conceivable that the present experiment may serve as a useful model for further studies on inner ear changes related to endolymphatic hydrops and Ménière's disease.

Animals↗

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↗