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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
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↗
PubMed1981

Temporal bone characteristics in Meniere's disease.

The petrous portion of the temporal bone in patients with Meniere's disease differs from that of healthy individuals mainly in its lack of periaqueductal pneumatization and its consequently short and narrow vestibular aqueduct. Diminished pneumatization may have an impact upon the tomographic reproducibility of the aqueduct. A total lack of periaqueductal pneumatization is prevalent in long-standing Meniere's disease. Tomography may serve as a tool by providing a basis for the choice of surgical procedure. Roentgenologic and histologic studies have indicated that the pars rugosa of the endolymphatic sac in normals mainly is housed inside the distal part of the vestibular aqueduct. In patients with Meniere's disease, the sac might be located outside the aqueduct and therefore deprived of the functions of the loose and highly vascular tissue normally surrounding it within the aqueduct. This might influence the total vascular supply of the sac, thereby interfering with its resorptive and immunodefensive functions.

Endolymphatic Sac↗
PubMed1979

Lymphocyte-macrophage activity in the endolymphatic sac. An ultrastructural study of the rugose endolymphatic sac in the guinea pig.

The irregular epithelial layer which delimits the intermediate part of the endolymphatic sac, and the surrounding perisaccular tissue, were examined morphologically in the guinea pig by transmission electron microscopy. Specialized areas of the epithelium which have previously been designated as "non-vascularized epithelial processes" (NVP) were constantly observed. These proliferative areas showed a close topographical relation to the free luminal cells and contained an abundance of lymphoid cells. Lymphocytes and macrophages were intimately associated with each other in a manner similar to that seen in these two types of cells in antigen-stimulated lymphoid tissues. There was a marked degeneration and phagocytosis of cells. The richly vascularized perisaccular tissue was rich in plasma cells, monocytes, mast cells and lymphocytes. The latter could be seen to migrate through the endothelial cells in the thin post-capillary venules into the sac tissue. The authors consider that the endolymphatic sac plays a role as an immunological defence organ for the internal ear. A hypothetical model concerning circulation and turnover of certain of the free intraluminal cells in presented.

Animals↗
PubMed1979

The vascular supply of the endolymphatic sac.

The vascular anatomy of the endolymphatic sac in guinea pigs was examined following intravascular injection of silicone rubber (Microfil). Methacrylate resin of low viscosity (Mercox) was used to obtain vascular corrosion casts for scanning electron microscopy, which allowed more accurate differentiation between arteries and veins. The extensive vascular system around the sac comprises both arteries and veins, as well as lymphatic vessels. The arterial supply is derived mainly from the posterior meningeal artery in the posterior cranial fossa. In some cases a small artery also leads to the sac from the posterior vestibular artery in the labyrinth (in 7 of the 35 animals investigated). It courses together with the vein of the vestibular aqueduct along the walls of the endolymphatic duct. The blood is drained over the intermediate portion of the endolymphatic sac, which becomes lodged in a rich meshwork of capillaries, venules, veins and a few small arteries. A few venous trunks from both sac walls fuse with the vein of the vestibular aqueduct, which drains blood from the vestibule to the sigmoid sinus. Scanning electron microscopy also revealed numerous anastomosing vessels within bone channels with adjacent bone marrow sinusoids, which also probably contribute to the vascular supply of the endolymphatic sac.

Animals↗
PubMed1978

The electrical potential difference and impedance between CSF and blood in unanesthetized man.

The electrical potential difference (PD) between cerebrospinal fluid (CSF) and blood has been studied extensively in animals. To obtain data from man the PD and impedance were recorded from the lumbar subarachnoid space of thirteen unanaesthetized patients with a presumably normal blood--brain barrier. The spontaneous PD ranged from 1 mV to 5 mV, CSF positive to blood. Hyperventilation and CO2-inhalation changed the PD with a mean slope of deltaPD/deltapHa of --4.16 mV/pH. The CSF-blood PD in unanaesthetized man is similar in direction to that found in dogs, goats and rats, but its sensitivity to change in arterial pH may be less.

Adult↗
PubMed1977

The surgical anatomy of the endolymphatic sac.

The endolymphatic sac (ELS) and vestibular aqueduct (VA), which play a notable role in the pathogenesis of endolymphatic hydrops and Meniere disease, were identified in all anatomic and tomographic materials. More than 100 temporal bones were used for microdissection, tomography, and plastic molds. Normal subjects and Meniere disease patients were studied tomographically (N = 63) and observed during ELS surgery (N=49). In Meniere disease there is, with increassing duration of diseases, a decrease in the periaqueductal and opercular air cell pneumatization, with a concomitant shorter and straighter VA. This correlates with a decreased ELS luminal patency, and a more inferiorly positioned ELS. These factors help to explain both the difficulties of visualizing the VA by tomography in Meniere disease as well as the occasional difficulties reported by others in satisfactorily identifying the ELS at sac surgery. All observations are made from the surgeon's viewpoint to enhance clinical identification of the ELS.

Adult↗
PubMed1977

Urethral pressure profile in prostatic surgery.

Urethral pressure profile measurements were performed in 45 men suffering from micturation disturbances with the aim of evaluating the diagnostic aid of the procedure as compared to conventional urodynamic evaluation. The urethral pressure profile seems to be of value in visualizing the diseases of the prostate and the bladder neck, but it is of no definite aid except for postprostatectomy incontinence.

Humans↗