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Biomedical subjects

H Rask-Andersen

Publications and source records attributed to H Rask-Andersen.

At least 109 records · Page 6Linked to original sources
PubMed1977

Dynamics of upper urinary tract. I. An electrophysiologic in vivo study of renal pelvis in pigs: method and normal pattern.

Under halothane anesthesia, peroperative electromyography of the pelvis and ureter together with intrapelvic pressure and urine flow were recorded in 11 pigs; the electromyography was by bipolar extracellular leads. Pressure waves of low amplitude, synchronous with action potentials from leads placed most proximally in the pelvis, preceded action potentials registered by distally placed leads. Transmission of the action potentials from the pelvis to the ureter took place with a constant transmission velocity but the transmission ratio varied from 1:1 to 6:1. Ureteral electric activity was time-related to the urine bolus. The transmission velocity was smaller in the pelvis than in the ureter and seemed to accelerate caudally. Thus, there is electromyographic evidence that the renal pelvis controls ureteric activity and that this pacemaker function is mediated high up, most proximally, in the renal pelvis.

Action Potentials↗
PubMed1977

Dynamics of upper urinary tract. II. An electrophysiologic in vivo study of renal pelvis in pigs: analysis of the modality of pelvic activity during normal hydration and diuresis.

Renal pelvic function of Danish Landrace pigs under anesthesia was analyzed during "normal" and forced diuresis. Measurements were made of intrapelvic pressures, electromyogram recordings were taken from the pelvis and ureter, and bolus formation was followed. During constant diuresis, pelvic activity displayed a dominant frequency which varied between individuals. When pressure rose or fell, pelvic activity increased or decreased in proportion to the speed rather than the extent of the pressure change. Thus, after furosemide administration urine flow increased and pelvic pressure rose; and in association with the pressure rise, pelvic activity increased significantly when mean pelvic activity in the phase of steep pressure rise was compared with the mean activity over the last 5 min of the observation period before induction of diuresis. Thereafter, pelvic activity decreased despite maintenance of a higher pressure plateau than that in the initial low diuresis observation period. This mode of function can be explained by reference to the characteristics of smooth muscle. Postulation of a specific pacemaker is unnecessary.

Animals↗
PubMed1976

Incomplete ureteral duplication. Electromyographic and manometric investigation.

Studies were made peroperatively in a patient with incomplete ureteral duplication. Bipolar extracellular EMG-leads were taken from both pelvices, both ureteral segments and from the common ureter. Simultaneously pressure measurements were made in the pelvices. Function of the two pelvi-ureteral units were shown to be autonomous. Simultaneous action potentials and pressure waves were observed in each pelvis. Not every pelvic impulse was transmitted to the corresponding ureter, but when transmission did occur, the conduction rate was constant. Impulses from both ureteral branches were conducted distally to the common ureteral trunk, but impulses from the dilated segment had not the same quality (amplitude) as those from the non-dilated segment. Antiperistalsis was not observed. There was a measurable pressure difference between the two segments.

Action Potentials↗
PubMed1976

Experimental hydronephrosis. An electrophysiologic investigation before and after release of obstruction.

Pelvi-ureteric function was studied in pigs with experimental urinary tract obstruction, and again, 5 weeks after relief of the obstruction. Study parameters comprised EMG records taken from pelvis and ureter, measurements of intrapelvic pressure and urine flow, and some supplementary studies of renal function. Total obstruction of 5 and 6 weeks duration induced by cuffing the proximal ureter occasioned severe hydronephrosis and renal failure. Pelvic peristaltic activity was of low frequency, and abnormality was clearly more marked after the longer period of obstruction. There was, for example, some preservation of pelvi-ureteric synergism at 5 weeks, but at 6 weeks ureteric activity was wholly autonomous. Pelvic function was similarly isolated, and non productive. Inspection 5 weeks after reconstruction by pelvis resection and neo-anastomosis of the ureter showed continued absence of renal function and no restitution of normal peristaltic patterns. Partial obstruction, effected by implantation of the ureter in the psoas muscle, induced mild pelvic dilatation and impaired renal function, but there were only minor signs of disruption of normal anterograde pelvi-ureteric activity - irregularities, pauses in activity, and double activity complexes. When the ureter was freed functional patterns returned to normal. Both during obstruction and after relief, pelvic pressure increases during forced diuresis were the equivalent of or lower than the pre-determined norm. Cautery at the pelvi-ureteric junction destroyed the musculature and induced a progressive (fibrous stenosis. There was progressive dissociation of pelvi-ureteric activity, total when obstruction was total in which case ureteric activity was only autonomous, and partial when obstruction was partial in which case varying degrees of synergism and autonomous activity were seen. Successful reconstruction (pelvic resection and neo-anastomosis of the ureter) restored an apparent synergism in pelvi-ureteric function.

Animals↗
PubMed1976

Dynamics of upper urinary tract in man. Peroperative electrophysiological findings in patients with manifest or suspected hydronephrosis.

In 31 patients undergoing surgery in treatment of hydronephrosis, peroperative pelvic pressure measurements were made. EMG records were taken from pelvis and ureter, and occasional measurements of urine flow were made. In 6 instances these studies were also made in the contralateral "normal" kidney, but in 2 of these patients the diseased kidney was not studied. Pelvic pressure during antidiuresis in these 6 "normal" kidneys was about 5 mmHg, and pelvic activity of frequency 5/min. Pelvi-ureteric impulse transmission was anterograde and conduction times were constant. Conduction ratios varied. During forced diuresis mild pelvic pressure rises were seen together with transient increase in pelvic activity over the period of pressure increase. In the studies of hydronephrotic kidneys no significant differences were seen in pelvic pressure of frequency of pelvic activity compared with the "normal" kidney studies, but impulse transmission was markedly disturbed, manifest by varying conduction times, and, on occasion, total dissociation of activity within the pelvis, and between the pelvis and ureter. The more severe the degree of hydronephrosis, the more marked the disturbance. The findings are similar to those made in experiments with pigs after establishment of varying degrees of urine flow obstruction.

Action Potentials↗
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

Stereocilia-like structures in the endolymphatic sac in Ménière's disease and acoustic neuroma.

The vestibular aqueduct was surgically removed in 3 patients undergoing labyrinthectomy due to severe Ménière's disease (MD). Stereocilia-like structures were found in the luminal contents of the endolymphatic sac (ES) in all of these patients. The ES from 18 patients with acoustic neuroma were used as controls. In 1 of these, numerous stereocilia-like structures were found in the ES and in 3 additional patients, a few isolated cilia-like structures were disclosed. The findings may suggest an ongoing hair cell degeneration in the inner ear that is more advanced in patients with MD. The data also suggest that the endolymphatic duct is patent and that a longitudinal flow of endolymph also occurs in patients with MD.

Adult↗
PubMedDate not supplied

Tinnitus and translabyrinthine acoustic neuroma surgery.

The purpose of this investigation was to study the effects of translabyrinthine acoustic neuroma surgery on tinnitus in a consecutive sample of patients operated on between 1988 and 1994 in Uppsala (Sweden). A postal questionnaire was returned by 141 patients, yielding a 90% response rate without reminder. The results showed that tinnitus was experienced by 70% of the patients before surgery and 60% after surgery. In general, low degrees of tinnitus distress were found, which was confirmed by the questionnaire results. Ratings of tinnitus distress after surgery, using the Klockhoff and Lindblom grading system, showed that 48% had tinnitus of grade I, 46% of grade II, and 6% of grade III. Pre- and postsurgery grading of distress did not change significantly. There was a 35% risk for developing tinnitus when no preoperative tinnitus was present and a 15% chance that tinnitus disappears when present preoperatively.

Adult↗
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.

Animals↗
PubMedDate not supplied

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↗
PubMedDate not supplied

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↗