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Biomedical subjects

H Rask-Andersen

Publications and source records attributed to H Rask-Andersen.

At least 91 records · Page 5Linked to original sources
PubMed1976

Development of a probe for endoureteral investigation of peristalsis by flow velocity and cross section area measurement.

A probe system for measurement of ureteric flow velocity and ureter cross section area is described. The flow velocity transducer is placed at the tip of a conventional 4-F ureteric catheter. The cross section transducer consists of two circular electrodes at an interval of 4 mm, mounted on the catheter just behind the flow velocity transducer. In vitro calibration established voltage as a function of flow velocity according to Kings law. Stability was excellent (0-point drift less than 1%/hour). Response time for flow rise was 0.02 second, and for flow fall 1.0 second. Variations of the ambient temperature at constant flow showed a margin of error in flow determination of 10 to 15%/1 degrees C temperature variation. In vitro calibration of the cross section transducer established linear correlation between voltage and tube diameter, but limited by the actual interelectrode interval. Probe displacement from tube axis gave an error of up to 10%. In vivo studies were made in anaesthetized pigs. The probe did not affect ureter peristalsis. Flow velocities ranged from 0 to 5 cm/second and ureter cross sectional areas between 0 and 0.2 cm2. Further developments in the measuring system are discussed.

Animals↗
PubMedDate not supplied

Human cochlear aqueduct and its accessory canals.

The anatomy of the adult human cochlear aqueduct and its surrounding structures, and their normal variations at tomography, microdissection and plastic molding are described. The mean length of the aqueduct is 12.9 mm and the mean width of its funnel-shaped external aperture 4.2 mm. The mean width of the narrowest portion is 0.14 mm. No difference in aqueductal width was found between the youngest and oldest age groups. Complete bony obstruction was revealed at microdissection in 3 out of 82 specimens. In the remaining 79 the entire aqueduct was patent. The aqueduct usually runs parallel to the internal auditory canal when seen from above, and the AP projection is therefore most suitable for tomography. At tomography the entire aqueduct was visualized in 60% of the specimens. The isthmic portion was not visible in 40%. Major reasons for nonvisualization of the entire aqueduct are: 1) a luminal width less than 0.1 mm, 2) a high jugular fossa, 3) a posteriorly directed aqueductal convexity (10%), and 4) bony obliteration (4)%). Accessory canals close to and often wider than the aqueduct may complicate tomographic evaluation of the aqueductal patency. Nonvisualization of the aqueduct at tomography does not necessarily indicate nonpatency.

Adult↗
PubMedDate not supplied

Human endolymphatic duct: possible mechanisms of endolymph outflow.

The ultrastructure of the normal human endolymphatic duct (ED) was observed by transmission electron microscopy. The role of the epithelium, the various regions of the subepithelial space, and vasculature in the resorption of endolymph was morphologically studied in order to generate testable hypotheses of human ED function. These hypothetical mechanisms of endolymph outflow at the level of the ED are a passive transcellular movement of water across the epithelium, driven by an osmotic gradient created by a subepithelial organic matrix; an active transcellular ion exchange with a passive transepithelial outflow of water, which stresses the importance of the dilated lateral intercellular spaces; and an active transcellular vacuolar endolymph outflow, whereby high molecular weight substances are removed by the ED. These mechanisms may be useful in designing experimental studies of the ED and in interpretation of retrospective light microscopic and transmission electron microscopic studies of patients with Meniere's disease.

Adult↗
PubMedDate not supplied

Human endolymphatic sac: morphologic evidence of immunologic function.

The ultrastructure of ten normal human endolymphatic sacs (ES), fixed immediately after death and obtained at autopsy, was observed by transmission electron microscopy. The roles of the epithelium, subepithelial space, vasculature, and ES leukocytes were morphologically studied to evaluate possible immunologic functions of the human ES. In addition, five intraosseous ES biopsies from patients undergoing translabyrinthine acoustic neuroma resection were studied using the immunoperoxidase technique to identify specific leukocyte subpopulations. Evidence of phagocytic activity included the presence of phagocytic epithelial cells, monocytes, macrophages, and polymorphonuclear leukocytes. Immune surveillance was suggested by intraepithelial and subepithelial T-lymphocytes, numerous fenestrated blood vessels, and the presence of a homogeneously staining substance within the lumina of ES epithelial tubules. No B-lymphocytes were found. The findings support the existence of a local immune system of the normal human inner ear.

Adult↗
PubMedDate not supplied

Immunodefence of the inner ear? Lymphocyte-macrophage interaction in the endolymphatic sac.

Owing to their proximity to areas exposed to infection, the sensory organs of the inner ear are probably dependent on an efficient antimicrobial defence. The longitudinal flow of endolymph to the endolymphatic sac may be of major importance in this context. Substances entering the ear can be automatically carried to the distal part of the endolymphatic duct, where lymphoid cells are present and endolymphatic phagocytosis occurs. In the intermediate part of the epithelium of the sac morphological signs marking the incoming substances are present. A vigorous interaction between lymphocytes and macrophages, similar to that observed in antigen-activated lymphoid tissue, may be seen. The sac is here surrounded by a rich network of lymphatic capillaries and blood vessels.

Animals↗
PubMedDate not supplied

The role of the endolymphatic sac in statoconial formation and degradation.

In the present investigation we studied the morphology o the endolymphatic sac in guinea pig fetuses (age 20-, 30-, 45-, 60-days-old and newborns). Twenty-day and 30-days-old guinea pig fetuses often displayed small prismatic or hexagonally shaped granules, presumably representing miniature otoconia. The granules appeared freely in the lumen of the endolymphatic sac as well as incorporated in the cytoplasm of the freely floating cells or macrophages. The origin of these "sac otoconia' as well as the possible role of the endolymphatic sac in statoconis turnover and metabolism is discussed.

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A freeze-fracture study of receptor axons and Schwann cells in the human olfactory mucosa.

Electron micrographs of freeze-fracture replicas from the human olfactory mucosa were analysed regarding the structure of the axons of the olfactory receptor cells. In the lamina propria, numerous axons were generally invested with one Schwann cell. The ensheathed axons were often found in close contact with one another. Membrane specializations were not found at these sites, nor were tightening membrane junctions observed in the mesaxons. The Schwann cell plasmalemma exhibited caveolae, whose neck was surrounded by uniformly sized intramembranous particles evenly distributed over the axolemmal fracture planes. There was a marked difference in particle density between the P face (about 850/micron 2) and the E face (about 180/micron 2).

Axons↗
PubMedDate not supplied

Effect of labyrinthectomy on the endolymphatic sac. A histological, ultrastructural and computer-aided morphometric investigation in the mouse.

A time sequence study of the effect of hemilabyrinthectomy on the endolymphatic sac was performed in mice. Light and transmission electron microscopy of the sac showed significant morphological changes of the epithelial lining and adjacent structures. Initially (2 and 4 days post-labyrinthectomy) the sac lumen was collapsed, but later (7 days post-labyrinthectomy) it was dilated or 'ballooned' and filled with a darkly staining homogeneous substance. This substance, which has been identified histochemically as a proteoglycan, appeared to be secreted from the epithelium of the endolymphatic sac. This finding suggests that the endolymphatic sac may be capable both of absorbing and of secreting endolymph.

Animals↗
PubMedDate not supplied

The development of the endolymphatic duct and sac. A light microscopical study.

The development and maturation of the endolymphatic sac were studied in the CBA/CBA mouse. The otocyst is developed at gestational day 10 and the primitive endolymphatic sac is present as a large slit-like appendage at day 12 of gestation. At day 18 the endolymphatic sac is clearly detached from the rest of the otocyst, forming a true sac. The epithelial lining consists of only one layer of immature cells containing large vesicles. The endolymphatic sac is surrounded by a rich network of vessels. One day before birth, the epithelial lining is uneven and the first signs of differentiation into light and dark cells is visible. This situation is more pronounced 2 days post partum when the sac also seems to be filled with a stainable material. At day 6 post partum the otic capsule fuses around the sac, forming the vestibular aqueduct. At 14 days post partum the sac is mature, with clearly developed light and dark cells and widened lateral intercellular spaces, constituting the rugose epithelium. The lumen is filled with a stainable precipitate and a few free-floating cells.

Animals↗
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Cytochemical localization of Na-K ATPase in the guinea pig endolymphatic sac.

The light microscopical and ultracytochemical localization of Na-K ATPase (ouabain-sensitive, potassium-dependent p-nitrophenylphosphatase) in the guinea pig endolymphatic sac was studied by a newly developed lead citrate one step method. The cytochemical reaction product was detected in the epithelial cell layer of the endolymphatic sac at the light microscopical level. At the electron microscopical level, the reaction product was located to the basolateral plasma membrane of both the dark and the light cells. The results suggest that Na-K ATPase may play a role in the ion transport mechanism in the endolymphatic sac.

Animals↗
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Degradation of the homogeneous substance in the endolymphatic sac.

The accumulation and degradation of a homogeneous precipitate in the lumen of the endolymphatic sac (ES) was studied in mice. Filling of the endolymphatic sac was induced by surgical labyrinthectomy and the sacs were studied 1-8 weeks postoperatively. The initial phase (1-2 weeks postlabyrinthectomy) was characterized by filling of the ES with the homogeneous precipitate. The number of freely floating cells in the lumen was increased after two weeks. Three weeks postoperatively the ES lumen was generally clear, with apparently no stainable material. Ultrastructural analysis of the ES showed that this clearance of the endolymphatic space resulted from degradational activity in the epithelial cells initiated in the proximal portion of the sac. Breakdown of the homogeneous substance seemed to result from cellular ingestion with concomitant lysosomal digestion. Four weeks postoperatively cell clusters were observed subepithelially and were filled with densely staining precipitate, indicating that these cells or macrophages were involved in the turnover of the homogeneous substance in the ES. The functional significance of a degradational system of this substance in the ES is discussed.

Animals↗
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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↗
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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↗
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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↗