Biomedical subjects

H Rask-Andersen

Publications and source records attributed to H Rask-Andersen.

99 records · Page 6Linked to original sources

PubMedDate not supplied

The pre- and postnatal maturation of the epithelium in the endolymphatic sac. An electron microscopic survey.

The cellular development of the endolymphatic sac was studied in the CBA/CBA mouse, starting from day 10 of gestation following the different stages of maturation up to an adult age of one month. The first immature cylindrical cells lining the future sac in several cell layers are seen at day 12 of gestation. At day 18 of gestation, a true sac appears and a floccular precipitate is frequently found in its lumen together with signs of increased activity in the still immature epithelial cells. Approximately one day before birth the first signs of the future light and dark cells can be distinguished. At day 4 post partum the cells are more differentiated with some showing signs of secretory activity indicating that these cells start to function at this stage. Eight days after birth differentiation into distinguishable almost mature light and dark cells is seen. Two days later these epithelial cells have obtained a fully mature appearance. At 14 days after birth widened lateral intercellular spaces separating the epithelial cells can be visualized and a few free floating cells are found in the sac lumen. The sac epithelium is thus considered to have completed its maturation process at this stage.

Animals↗

PubMedDate not supplied

Intracellular changes in the endolymphatic sac after labyrinthectomy.

Intracellular changes within the lining epithelium of the murine endolymphatic sac were investigated following surgical labyrinthectomy. The light and the dark epithelial cells reacted differently. Some light cells showed altered morphology after labyrinthectomy. The smooth endoplasmic reticulum formed a tubular network in the apical cytoplasm which was contiguous with the extremely well developed rough endoplasmic reticulum. These light cells also contained numerous granules. Such cell modifications indicated a secretory potential in this type of light cells. The dark cells showed signs of increased activity, with an augmentation of endoplasmic reticulum and an increased electron density of the cytoplasm. The dark cells increased their luminal surface to such an extent that they frequently covered the luminal surface of neighbouring light cells. Our hypothesis is that the dark cells may, in some way, control the function of the light cells and in this way also the absorptive mechanisms of the endolymphatic sac.

Animals↗

PubMedDate not supplied

Time sequence of degeneration pattern of the organ of Corti after acoustic overstimulation. A light microscopical and electrophysiological investigation in the guinea pig.

In order to obtain information about the sequence of events leading to degenerative changes in the cochlea after acoustic trauma, a systematic LM study was performed in the guinea pig organ of Corti. The results were correlated with measurements of CAP N1 thresholds from the same animals. Twenty pigmented guinea pigs were used in the study. Ten of these animals were exposed to a 3.85 kHz pure tone with an intensity varying between 108 and 120 dB SPL for 22.5 to 360 min and were sacrificed after 4 weeks. Eight animals were exposed to 120 dB SPL for 22.5 min and sacrificed at regular intervals after exposure, viz. 5 min, 4, 24 h and 5 days. Prior to sound exposure the animals in the 4-week group were implanted with a permanent round window electrode for measurements of CAP N1 thresholds. The study indicates that the degeneration and reparative processes are not entirely completed after 4 weeks. The development of holes in the reticular lamina may result in further degeneration of cells bilateral to the initial maximum damage. Darkly stained cells seem to be activated in the reparative process in the organ of Corti. Local appearance of dendritic macrophages in the organ of Corti indicate the existence of a local mechanism for disposal of degeneration products from the organ of Corti. The retrograde degeneration of radial nerve fibres seems to be closely associated with that of the pillar cells. A close correlation between structural hair cell damage and CAP N1 threshold shift was found in the region of the organ of Corti corresponding to the exposure frequency. The TS 5 min, 4 h and 24 h after exposure showed a close correlation with swellings in the afferent nerve endings below the IHC in the area of maximum damage and basalwards.

Acoustic Stimulation↗

PubMedDate not supplied

Morphology of the endolymphatic duct and sac in the Mongolian gerbil.

A light microscopical study of the endolymphatic duct and sac of the Mongolian gerbil is presented. This animal model was studied because of its tendency to develop a condition of body fluid imbalance which may represent a hazard to the inner ear fluid environment. Particular stress is laid on the combination of the lack of an extraosseous endolymphatic sac and the presence of elastic tissue in the subepithelial space of the sac. These findings highlight the role of this structure for the regulation of the pressure within the inner ear. Lastly, a secretory process is proposed by which a homogeneous precipitate produced in the lumen of the sac can regulate volume and pressure changes.

Animals↗

PubMedDate not supplied

Cytochemical identification of secreted carbohydrates in the endolymphatic sac.

Carbohydrate complexes were investigated in the murine endolymphatic sac by means of histochemical techniques in normal untreated animals as well as after ethacrynic acid treatment. The light epithelial cells were classified into three different types: normal, granular and vacuolar. The granular and vacuolar cells were believed to secrete glycoproteins and/or proteoglycans, the presence of which was closely correlated with the component of the precipitate in the lumen of the endolymphatic sac. This finding suggested that the light cells not only absorb endolymph but may also be involved with secretory activity. Such a dual modality in function may have several important implications, since it suggests that the endolymphatic sac has both absorptive and secretory functions.

Animals↗

PubMedDate not supplied

Hyaluronan content in human inner ear fluids.

Histochemical analyses of the luminal contents of the endolymphatic sac in numerous mammalian species have indicated a presence of acid mucopolysaccharides or proteoglycans. In the present study, one of these substances, hyaluronan (hyaluronic acid; HA), in endolymphatic sac endolymph and vestibular perilymph in humans, was biochemically determined with a highly specific radioassay. A considerable variation in HA concentration was noted between the individual ES endolymph samples, with a mean value of 2.50 micrograms/g (range 0.00-10.86). In perilymph the HA concentrations were less variable and the mean concentration was 0.91 micrograms/g (range 0.56-1.51). The difference between endolymph and perilymph HA concentration was not statistically significant (p greater than 0.05). The ability of HA to interact with proteoglycans, thereby forming giant hydrophilic molecules, could be important for ES function. These molecules may create a swelling pressure which is resistant to compressive forces that under conditions of increased intracranial hydrostatic pressure otherwise could cause ES collapse and impaired function.

Adult↗

PubMedDate not supplied

Uptake of radioactive sulphur in the endolymphatic sac. An autoradiographic study.

Autoradiographic uptake of labelled sulphur (S35) in the endolymphatic sac was analysed after performing surgical labyrinthectomy and after systemic administration of glycerol and ethacrynic acid. Accumulation of radioactive substance was observed after surgical labyrinthectomy and associated with a deposition of stainable substance in the endolymphatic sac lumen. Increased activity was noted in the epithelial layer after administration of ethacrynic acid, whereas glycerol did not increase radioactivity in the endolymphatic sac despite the deposition of stainable substance therein. This fact was believed to depend on a too short time interval between the injection and the sacrifice of the animals, as well as a weaker concentration of the sulphated compound within the endolymphatic sac. The results suggest that the endolymphatic sac may secrete sulphur-containing substances presumably associated with a deposition of a stainable substance in the endolymphatic sac.

Animals↗

PubMedDate not supplied

The role of macrophages in the disposal of degeneration products within the organ of corti after acoustic overstimulation.

We analysed the ultrastructure of scavenger cells in the organ of Corti of 10 guinea pigs at five different intervals (5 min, 4 h, 24 h, 5 days and 28 days) after acoustic overstimulation. There was evidence of phagocytic cells only at 5 days after noise exposure. Dendritic macrophages were seen phagocytosing degenerating cells and debris in the tunnel of Corti and in the region of the outer hair cells. Transforming monocytes in this area and leukocytic accumulation within the spiral lamina vessel suggest that these cells may be derived from blood-borne monocytes. These cells may contribute to local disposal of intracochlear cell degeneration products and thus to healing of organ of hearing after induction of noise-induced damage.

Animals↗

PubMedDate not supplied

Ultrastructural characterization of otospongiotic lesions in re-embedded celloidin sections.

A technique of using re-embedded celloidin sections for ultrastructural analysis was used for the study of otospongiosis in human temporal bones. Celloidin sections stored in 80% alcohol with active lesions of cochlear otospongiosis were processed and re-embedded in epoxy resin. Semithin and thin sections were cut and analysed for a characterization of the ultrastructural cellular histopathology. The predominant cell types were found to be osteoblasts/osteocytes and macrophages. Lymphocytes were also noted but were rare. Several osteoblasts showed signs of active collagen and bone matrix production, indicative of ongoing new bone formation and repair. Macrophages often interacted physically to form cell clusters. The macrophages were frequently observed to endocytose the non-mineralized bone matrix as well as to degrade mononuclear cells presumed to represent osteoblasts. The observations may support the notion that increased osteolysis in active ostospongiosis is partly caused by a recruited osteoclast activity and partly by an impaired bone repair mechanism due to a macrophage digestion of osteoblast-deposited non-mineralized bone matrix. These two conditions may act in concert with cellular degradation of bone-producing cells.

Bone Resorption↗