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Biomedical subjects

H Rask-Andersen

Publications and source records attributed to H Rask-Andersen.

At least 55 records · Page 3Linked to original sources
PubMed1987

The endolymphatic sac in a mouse mutant with cochleo-saccular degeneration. Electrophysiological and ultrastructural correlations.

The response of the endolymphatic sac to a disturbance in endolymph homeostasis was investigated by examining the sac in a mouse mutant, viable dominant spotting, which is known to exhibit primary strial dysfunction and cochleo-saccular degeneration. The function of the vascular stria was assessed by measuring the endocochlear potential and the sacs were then studied by light and transmission electron microscopy. The endolymphatic sac was found to be morphologically abnormal in these mutants, the main abnormality being the presence of granular epithelial cells, which showed clear histological signs of secretory activity. A stainable precipitate, believed to be secreted by the granular cells, was observed in the lumen of the endolymphatic sac in the mutants. The findings strengthen the view that the sac is involved in the regulation of endolymph volume and pressure.

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↗
PubMed1987

Human endolymphatic sac: possible mechanisms of pressure regulation.

The ultrastructure of the normal human endolymphatic sac (ES) has been observed by transmission electron microscopy (TEM). The role of the epithelium, the various regions of the subepithelial space and the general anatomy of the ES in pressure regulation were morphologically studied to generate testable hypotheses of human ES function. Light microscopic (LM) and TEM evidence of pressure regulatory mechanisms by endolymph resorption, mechanical factors, and secretory activity are presented. These mechanisms may be useful in designing experimental studies of the ES, and in interpretation of retrospective LM and TEM studies of patients with Menière's disease.

Adult↗
PubMed1985

Basal lamina pathology of the utricle and endolymphatic duct in Ménière's disease.

Labyrinthectomy was performed in a patient with a 4-year history of Ménière's disease. The utricle and the proximal portion of the endolymphatic duct were studied using light and electron microscopy. The epithelium varied in height from squamous to columnar. The basal lamina lining the columnar epithelial cells showed marked thickening which was visible in the light microscope. Electron microscopy revealed that the basal lamina had a fibrillar structure. The basal lamina of adjacent blood vessels also showed pathologic thickening with similar fibrillar texture. The significance of basal lamina thickening in association with Ménière's disease is discussed.

Ear, Inner↗
PubMed1985

The lateral intercellular spaces in the endolymphatic sac. A pathway for fluid transport?

The lateral intercellular spaces (LIS) in the epithelium of the endolymphatic sac in different mammals were studied using light and transmission electron microscopy. The reason for the study was that widened LIS are known to occur in fluid transporting epithelia, where they may reflect transepithelial flux of water and solutes. Increased knowledge about LIS may lead to further insight into the mechanisms of endolymph resorption in the endolymphatic sac. The effects of various fixatives, fixation methods and osmolality, and also of surgical labyrinthectomy, on the ultrastructure of LIS were investigated. Widened LIS regularly occurred in the mammalian endolymphatic sac and seem to reflect an in vivo condition. It is thought that LIS may form a pathway for transepithelial water flow in the endolymphatic sac. A hypothetical model of the function of LIS during transepithelial fluid movement in the sac is presented.

Animals↗
PubMed1985

The ultrastructure of the human antral mucosa as demonstrated by freeze-fracturing.

The fine structure of the normal mucous membrane in the human maxillary sinus was investigated by means of the freeze-fracture technique. Special interest was directed to membrane structures in the epithelial cells. The morphology of tight junctions could be analysed. According to morphological criteria these junctions might be classified as "very tight". So called ciliary necklaces were well distinguishable. Their morphology seemed to be in concordance with the structure reported in other mammalian respiratory epithelia. Abluminally the epithelial cells frequently displayed abundant caveolae or micropinocytotic vesicles. The present investigation was performed as a preface to later studies on pathologically altered antral mucosa.

Cilia↗
PubMed1984

Human endolymphatic duct. An ultrastructural study.

The fine structure of the human endolymphatic duct was observed by transmission electron microscopy. Well-preserved specimens were obtained after fixation of inner ear tissue by perilymphatic perfusion. The morphologic findings seemed to be in accordance with earlier propositions that the human endolymphatic duct may be involved in endolymph resorption. The duct was found to contain otoconialike bodies, suggesting that the endolymphatic duct and sac in man may also play a role in the turnover of macular otoconia.

Adult↗
PubMed1984

Membrane structures in the pulp-dentin border zone. A freeze-fracture study of demineralized human teeth.

The membrane morphology of cells in the pulp-dentin border zone in human teeth was scrutinized by means of the freeze-fracture technique. The tissue was fractured and replicated after mild demineralization in Na-EDTA. This procedure did not seem to influence the preservation of the tissue significantly. The odontoblastic cell bodies and their long processes lying within the predentinal and dentinal tubules were exposed. The technique made it possible to analyze the structural features of the apical part of the odontoblastic layer, including the 'terminal bar' region. This area exhibited large, irregularly shaped gap junctions. In some regions clusters of many small membranous pits or caveolae apparently representing pinocytotic vesicles were seen. The odontoblastic process displayed membrane protuberances projecting outward and abutting the inner tubular wall. In the predentinal and the adjacent dentinal regions, fine-caliber fibers (approximately 0.1-0.4 micron in diameter), presumably nerves, appeared in intimate relationship with the odontoblastic cell processes. At these sites the cell membrane displayed aggregations of membrane-associated particles, presumably gap junctions.

Adolescent↗
PubMed1984

Membrane junctions between odontoblasts and associated cells. A freeze-fracture study of the human odontoblastic cell layer with special reference to its nerve supply.

The relationship between odontoblasts and adjacent cell structures within the odontoblastic cell layer was analyzed by means of the freeze-fracturing technique. Two principal forms of interodontoblastic cell structures were found. The first was tubular or thread-like in appearance, having a general diameter around 0.1-1.0 micron. From morphological criteria these were believed to represent small, unmyelinated nerve fibers. The second type of cell structure found between odontoblasts was more irregular and heterogeneous in outline, and often lamellar or branched. These slender formations sometimes proved to constitute cellular projections from adjacent odontoblasts or neighboring, subodontoblastic fibroblasts. Both the nerve-like fibers and the irregular branched cells between the odontoblasts showed morphological contact areas with odontoblastic cell bodies. At these sites the intracellular distances were reduced, and characteristic gap junctional complexes occurred. Nerve ending specialization or membrane structures indicating the presence of chemical synapses on the odontoblastic cell surface were not observed.

Adolescent↗
PubMed1984

The ultrastructure of the human endolymphatic duct.

The fine structure of the human endolymphatic duct as observed at transmission electron microscopy (TEM) is described. After fixation of inner ears by perilymphatic perfusion adequately preserved tissue specimens were obtained. Our morphological findings seem to be in accordance with the earlier proposition that the human endolymphatic duct may be involved in endolymph resorption. The duct was found to contain otoconia-like bodies, suggesting that the endolymphatic duct and sac, may play a role in the turnover of macular otoconia.

Adult↗
PubMed1984

Otoconia degradation.

During certain stages of mammalian inner ear development, small crystallized bodies which resemble otoconia may be found in the endolymphatic sac. In order to examine whether the endolymphatic sac plays any part in the process of degradation and dissolution of otoconia, we made an electron-microscopic examination on the endolymphatic sac of fetuses and adult guinea pigs injected with streptomycin sulfate (SM). In 30-day-old fetal guinea pigs we found miniature otoconium-like bodies (OLBs) in the endolymphatic sac and a giant OLB in the endolymphatic duct. In adult animals we found no otoconia in the endolymphatic sac following SM intoxication. However, the results suggested that both the dark cells of the utricle, as well as the non-sensory epithelium of the saccule, may be engaged in the absorption and dissolution of otoconia.

Animals↗
PubMed1983

Membrane junctions in the subodontoblastic region. A freeze-fracture study of the human dental pulp.

The morphology of the subodontoblastic region in the human dental pulp was analysed using the freeze-fracturing technique. Multiple areas of focal intercellular junctions were found between subodontoblastic fibroblasts (or Höhl's cells). The connections were of the gap junction type. Similar junctions were observed between subodontoblastic cells and small-calibre (0.10-0.20 microns) fibres, presumably nerves. Tight junctions were not observed.

Adolescent↗
PubMed1983

The blood capillaries in the subodontoblastic region of the human dental pulp, as demonstrated by freeze-fracturing.

The microvasculature of the subodontoblastic region in the human dental pulp was studied, using freeze-fracturing. This technique allows an analysis of the fine structure of the vascular endothelium with special reference to the membrane structure. The blood capillaries were noted to be of the non-fenestrated or continuous type, although a few fenestrated vessels were observed. The endothelial plasmalemma often exhibited bundles of fibrillar structures, presumably myofilaments. There was a relatively large number of micropinocytotic vesicles and the interendothelial spaces were closed juxtaluminally by tight junctions (zonulae occludentes). The junctions appeared mostly as two to four strands, seen as ridges or grooves on the cell membrane. Thin-walled, irregular, tissue channels lacking the typical, blood-vessel configuration were disclosed. These vessels were believed to represent lymphatics.

Capillaries↗
PubMed1983

The fenestrated blood vessels of the endolymphatic sac. A freeze-fracture and transmission electron microscopic study.

The fenestrated blood vessels surrounding the endolymphatic sac in guinea pigs were investigated with the help of freeze-fracturing. The technique exposes the structure and distribution of vascular pores as well as interendothelial bridges or tight junctions between vascular endothelial cells. It is possible to get a three-dimensional comprehension of the vascular structure which can be compared with that of conventional transmission electron microscopy (TEM). Discontinuity in the junctional elements as seen in some endothelial layers and the high number of fenestrations organized in geometric patterns, as well as the abundant, randomly distributed micropinocytotic vesicles seem to bear out the theory that the endolymphatic sac is one of the most metabolically active parts of the inner ear and may be involved in the turnover of endolymph.

Animals↗