Biomedical subjects

J Rostgaard

Publications and source records attributed to J Rostgaard.

At least 19 recordsLinked to original sources

PubMed1999

A note about retinal structure and visual acuity. A light microscopic study of the cones in fovea centralis.

PURPOSE: Production of reliable sections of fovea centralis of primate retina. METHODS: Rhesus monkey eyes were processed using a new technique known to minimize artefacts and cell-shrinkage in other tissues. An in vivo vascular perfusion-fixation technique with an isotonic fixative followed by a process of slow infiltration with small increments in concentrations were used. RESULTS: Tangential 1 microm thick serial-sections showed a very good morphology. An average cone-to-cone-center distance of 3.8 microm in the central part of the fovea centralis was found. A cone-to-cone-center distance of 2.2-2.6 microm is suggested in the literature. CONCLUSION: In spite of the limited study we believe that the new technique has resulted in less tissue shrinkage. Our results are discussed in relation to maximal possible resolution of the eye. Our calculations (for green light) support the idea that the structure of the fovea centralis and the refractive media of the eye are developed close to perfection.

Animals↗

PubMed1999

The endolymphatic sac, a potential endocrine gland?

A previous investigation indicated that the chief cells of the endolymphatic sac produce an endogenous inhibitor of sodium re-absorption in the kidneys, which has tentatively been named "saccin". In this study, the ultrastructure of the endolymphatic sac and in particular the chief cells is described, demonstrating that this organ fulfils the morphological criteria of a potential endocrine gland. Accordingly, the chief cells are shown to exhibit all the organelles and characteristics of cells that simultaneously synthesize, secrete, absorb and digest proteins.

Animals↗

PubMed1997

Electron microscopic demonstrations of filamentous molecular sieve plugs in capillary fenestrae.

The permeability of capillaries is usually explained with reference to "small pores," permeable to water and small solutes, and "large pores," permeable to proteins. Fenestrated capillaries are far more permeable to water and small solutes than nonfenestrated capillaries; moreover, the permeability is highest in the capillaries with the most fenestrae. This suggests that the small pores reside in the fenestral diaphragms; however, no such pores have been illustrated using electron microscopy. In an attempt to clarify this controversy, fenestrated capillaries in the small intestine, stomach, and kidney of the rat were reinvestigated by electron microscopy. A new method of vascular perfusion-fixation was employed, which included the use of glutaraldehyde dissolved in an oxygen-carrying blood substitute (fluorocarbon) and delivered by a peristaltic pump controlled by pressure feedback. The investigation disclosed a prominent endocapillary surface coat, about 50-100 nm thick, and the existence of bush-like filamentous sieve plugs in the fenestrae. Each filamentous plug was composed of 20-40 filaments, each filament measuring 300-400 nm in length and 5-10 nm in thickness. The filamentous plugs have tentatively been named fascinae fenestrae, because they resemble fascines and may also function as such.

Actin Cytoskeleton↗

PubMed1997

Effect of cyclosporine during initiation of transplant arteriosclerosis. An ultrastructural study in the aorta-transplanted rabbit.

The immunosuppressant cyclosporine protects against the development of experimental transplant arteriosclerosis. To investigate the mechanism underlying this effect, aorta-allografted rabbits were randomly assigned to cyclosporine (n = 6) in the human therapeutic range or to its vehicle (n = 5). Perfusion fixation was performed 2 weeks after the transplantation, followed by light, scanning and transmission electron microscopy examination. Intimal proliferation was absent in native aortas, present in all grafts from vehicle-treated animals, and either absent or sparse in grafts from cyclosporine-treated rabbits. The endothelium of native aortas from both vehicle- and cyclosporine-treated rabbits was normal. Aortic allografts from cyclosporine-treated rabbits exhibited a normal endothelium with only a few adhering mononuclear cells, whereas aortic allografts from vehicle-treated rabbits exhibited an endothelial surface ranging from near-normal with only few adhering platelets and mononuclear cells, to an almost destroyed endothelium, lined with lymphocyte-like cells, monocytes/macrophages, platelets, erythrocytes and fibrin; in the subendothelial layer, mononuclear cells and smooth muscle cells were abundant. These results suggest that damage to the endothelial cells as well as invasion of lymphocytes, monocytes/macrophages and smooth muscle cells into the subendothelial space are important events during initiation of transplant arteriosclerosis, and that cyclosporine largely attenuates these early pathological changes.

Animals↗

PubMed1996

The inner ear produces a natriuretic hormone.

Cytoplasmic granules have been demonstrated in epithelial cells from the endolymphatic sac, an extraosseus part of the inner ear located in the posterior cranial fossa. Intravenously infused extracts from endolymphatic sacs in anesthetized rats elicited a potent natriuresis and diuresis without effects on blood pressure, glomerular filtration rate, or lithium clearance. Only a minor kaliuresis was observed. Extracts of dural tissue adjacent to the endolymphatic sacs had no effect. It is concluded that the endolymphatic sac contains as endogenous inhibitor of sodium reabsorption and could be the sensory organ/mediator of "cerebral" natriuresis. Furthermore, this substance, tentatively named saccin, may influence the homeostasis of the inner ear fluids and accordingly play a significant role in the pathogenesis of Mèniére's disease.

Absorption↗

PubMed1995

Surface morphology of the endolymphatic duct in the rat. A scanning electron microscopy study.

Following intracardiac vascular perfusion fixation of 8 rats with glutaraldehyde in a buffered and oxygenated blood substitute, the vestibular aqueduct and endolymphatic duct were opened by microsurgery of the resulting 16 temporal bones. Optimum preservation of the epithelium for scanning electron microscopy was attained by coating of the specimens with osmium tetroxide and thiocarbohydrazide followed by a continuous dehydration procedure. This technique permitted, for the first time, an investigation of the surface morphology of the epithelial cells in the endolymphatic duct. Three types of cells were identified with the scanning electron microscope. A polygonal and oblong epithelial cell was observed in the largest number throughout the duct, and in the juxtasaccular half of the duct, two additional types of epithelial cells were observed. The scanning electron microscopic observations are compared and discussed with reference to previous transmission electron microscopic studies of the endolymphatic duct.

Animals↗

PubMed1995

Fine structure of the endolymphatic duct in the rat. A scanning and transmission electron microscopy study.

To investigate the surface morphology of the endolymphatic duct epithelium, 8 rats were vascularly perfused with glutaraldehyde in a buffered and oxygenated blood substitute. Optimal preservation of the epithelium for scanning electron microscopy was attained by coating of the specimens with OsO4 and thiocarbohydrazide followed by a continuous dehydration procedure. Three types of cells were identified with the scanning electron microscope: A polygonal and oblong epithelial cell was observed in the largest number throughout the duct, whereas in the juxta-saccular half of the duct two additional types of epithelial cells were observed. The scanning electron microscopical observations are compared and discussed with reference to transmission electron microscopical observations of the endolymphatic duct.

Animals↗

PubMed1995

The suspensory ligament of the endolymphatic duct in the rat. An ultrastructural study.

Following optimized fixation and specimen handling, the endolymphatic duct was investigated by transmission and scanning electron microscopy. Tubular microfibrils, 10-12 nm thick and of indefinite length, occupied the subepithelial compartment abundantly and seemed to insert into the basal lamina of the epithelial cells of the duct and to merge with the bony wall of vestibular aqueduct thus forming a suspensory ligament of the endolymphatic duct. This ligament is suggested to protect the endolymphtaic duct from collapsing and to play a role in the mechanical protection of the vestibular apparatus from sudden increases in intracranial pressure. The capillaries and the aqueductal vein were located in intimate relationship to the epithelial cells. Both types of vessels were provided with fenestrations of the endothelial cells, supporting the proposal that the endolymphatic duct may be involved in the resorption of endolymph.

Animals↗

PubMed1994

Ultrastructure of Reissner's membrane in the rabbit.

The ultrastructure of Reissner's membrane in the rabbit is described following vascular perfusion-fixation of live, anesthetized and artificially respirated healthy animals. A new and improved technique of fixation is employed that includes a pressure feedback controlled peristaltic pump and an oxygen-carrying fixative. In ultrathin sections capillaries were observed between the two cell layers comprising Reissner's membrane. The mesothelial cells facing the scala vestibuli were connected by junctional complexes and neither pores nor discontinuities were observed in the cell layer. In the epithelial cells a well-developed tubulocisternal endoplasmic reticulum (TER) was noted. Computerized three-dimensional reconstruction documented the continuity of this TER, from prominent disc-shaped subsurface cisterns lining the luminal cell membrane to smaller subsurface cisterns lining the abluminal and lateral cell membranes, forming a transcellular canalicular pathway. The possible function of the TER in Reissner's membrane is discussed with reference to endolymph/perilymph homeostasis.

Animals↗

PubMed1994

Ultrastructure of the epithelial cells of the endolymphatic duct in the rat.

The ultrastructure of the epithelial cells of the endolymphatic duct in the rat is described, following vascular perfusion-fixation of live, anaesthetised and artificially respirated animals. The animals were fixed by means of a pressure feed-back controlled peristaltic pump and an isotonic perfusate-fixative containing glutaraldehyde and Dextran. The endolymphatic duct was isolated by microdissection after the perfusion-fixation, to omit the step of a demineralization procedure. The proximal, intermediate and juxta-saccular parts of the endolymphatic duct were embedded, sectioned and studied separately in the electron microscope. Postfixation in a solution containing OsO4 and potassium ferricyanide revealed a well-developed tubulo-cisternal endoplasmic reticulum (TER), not previously described. Serial sectioning and computerized three-dimensional reconstruction demonstrated a continuity of the TER through the cell from subsurface cisterns abutting on the apical cell membrane to subsurface cisterns abutting on the basolateral cell membrane. The TER resembles that found in solute transporting epithelia, e.g., renal proximal tubule, gall bladder, small intestine and choroid plexus. A fluid resorptive capacity of the epithelial cells of the endolymphatic duct is compatible with the fine structure revealed in the present study. Epithelial cells in the juxta-saccular part of the duct display morphological indications of a secretory activity; furthermore, multivesicular bodies were observed in the epithelial cells throughout the endolymphatic duct.

Animals↗

PubMed1993

Improvements in the technique of vascular perfusion-fixation employing a fluorocarbon-containing perfusate and a peristaltic pump controlled by pressure feedback.

A new improved technique for whole-body perfusion-fixation of rats and other small animals is described. The driving force is a peristaltic pump which is feedback regulated by a pressure transducer that monitors the blood-perfusion pressure in the left ventricle of the heart. The primary perfusate-fixative is composed of a blood substitute--13.3% oxygenated fluorocarbon FC-75--in 0.05 M cacodylate buffer (pH 7.4) with a 2% glutaraldehyde. The secondary perfusate-fixative is composed of 2% glutaraldehyde in 0.05 M cacodylate buffer (pH 7.4) with 20 mM CaCl2. A double-barrelled, self-holding cannula is used to cannulate the heart; the outer and inner barrels of the cannula are connected to the peristaltic pump and to the pressure transducer, respectively. The tissue oxygen tension in the rat is monitored by a subcutaneous oxygen electrode. Measurements showed that tissue hypoxia/anoxia did not develop before or during the perfusion-fixation. Thus, the technique permits study of specimens which do not exhibit fixation gradients and do not contain cells fixed in a state of asphyxia. This is substantiated by electron micrographs of cells from different organs, revealing new fine structural elements. By adding oxygenated fluorocarbon to glutaraldehyde perfusate-fixatives, enough oxygen is made accessible for cellular respiration as well as for the oxygen-consuming chemical reactions of glutaraldehyde with the tissue. Data on anaesthesia, operative manoeuvres, mechanical components of the system, preparation of fixatives and flow of the perfusate-fixatives are furnished and discussed.

Animals↗

PubMed1993

Ultrastructure of the endolymphatic duct in the rat. Fixation and preservation.

Ten rats were vascular-perfused at subphysiologic as well as physiologic pressures, 80 mmHg and 120 mmHg, respectively, employing a pressure feed-back controlled peristaltic pump and an isotonic perfusate/fixative with colloids (2% Dextran) and a hypertonic perfusate/fixative without colloids, 300 and 530 mOsm, respectively. In both experiments the endolymphatic duct and sac were isolated by microdissection after primary fixation. When comparing micrographs from the two experiments we observed that rats perfused at low pressure in isotonic fixative with colloids added had non-dilated lateral intercellular spaces and a subepithelial ground substance loaded with uniformly arranged microfibrils, not previously discovered. In rats perfused at high pressure in hypertonic fixative with no colloids added, we observed an edematous state in the subepithelial space between the solid bony aqueduct and the endolymphatic duct, with a concomitant derangement of previously well organized microfibrils. Furthermore, the epithelium was quite clearly displaced from the capillaries, the intercellular spaces were widely dilated and the endolymphatic duct was compressed into its lumen. Methods of fixation and current theories of endolymph resorption by the endolymphatic duct are discussed.

Animals↗

PubMed1992

The use of autologous fibrin adhesive in skin transplantation.

A method for preparing concentrated fibrinogen for use in autologous fibrin adhesive is described. The adhesive was used in seven patients with eight chronic leg ulcers. The ulcers were divided into two equal sections, and the adhesive was used to seal split-thickness skin grafts in one section, while no adhesive was used to seal the grafts in the other section of the ulcer. The strength of adhesion was measured 3 1/2 minutes after transplantation of a 1-cm2 test split-thickness skin graft. In the sealed grafts, the breaking strength varied from 12 to 26 gm. In the unsealed transplants, the strength was less than 5 gm. The take of the meshed split-thickness skin grafts was equal in the sealed and the unsealed areas, varying from 90 to 100 percent. Biopsies taken on day 7 showed a splitting between graft and recipient bed in half the unsealed grafts; none of the sealed grafts showed splitting, indicating a more stable graft in the sealed areas. Biopsies taken on day 21 showed no difference between sealed and unsealed grafts.

Female↗

PubMed1990

Three-dimensional organization of a transcellular tubulocisternal endoplasmic reticulum in epithelial cells of Reissner's membrane in the guinea-pig.

The ultrastructure of the epithelial cells of Reissner's membrane (membrana vestibularis) in the guinea-pig is described following vascular perfusion with glutaraldehyde of live, anaesthetised and artificially respirated animals. Postfixation in a solution containing OsO4 and potassium ferricyanide revealed a well-developed tubulocisternal endoplasmic reticulum, not previously described, the continuity of which has been mapped by serial sectioning and reconstruction. Large disc-shaped subsurface cisternae lining the cell membrane, but separated from it by a space approximately 10 nm wide, are in continuity with the smooth endoplasmic reticulum, forming an elaborated transcellular canalicular pathway. This structure is compared to that found in solute-transporting epithelia, e.g., renal proximal tubule, gall bladder, small intestine and choroid plexus. The fixation method used in the present study is compared to other techniques used for preservation of Reissner's membrane. Each epithelial cell of Reissner's membrane is endowed with one kinocilium, one to four multivesicular bodies, and a number of intercalated bodies. The functional significance of the canalicular pathway is discussed.

Animals↗

PubMed1990

Mesothelium of Reissner's membrane in guinea pigs: an electron microscopic study.

The mesothelial cells of Reissner's membrane in guinea pigs were found to be connected by junctional complexes. No cell discontinuities or gaps were observed by scanning or transmission electron microscopy. These results are not in accordance with previous studies. They were achieved by in vivo vascular perfusion fixation, handling of cochleae in protective specimen carriers, thiocarbohydrazide treatment and continuous dehydration. Findings in the present study indicate that the interepithelial space between the epithelial and mesothelial cell layers constitutes a specific compartment which must be considered when examining solute transport over Reissner's membrane.

Animals↗

PubMed1989

Ultrathin sectioning for electron microscopy: the distilled water in the knife trough may extract phosphatase reaction products from the sections.

During an electron microscopical study of the localization of the nucleoside diphosphatase IDPase in Reissner's membrane of the inner ear, it was discovered that the distilled water in the knife trough produced an annoying artefact. It dissolved all the lead phosphate reaction product from the sections, and thus converted a positive phosphatase reactivity to a false negative one. The water in the knife trough had a pH of approximately 5.4. Calculations showed that this is an expected acidity, if CO2 in the air equilibrates with distilled water, and that there is 200,000 times more acid in the trough than necessary to dissolve all the reaction product from a ribbon of ultrathin sections. Experiments showed that the artefact could be avoided by adjusting the pH to neutrality with dilute ammonia.

Acid Anhydride Hydrolases↗

PubMed1985

Critical-point drying versus freeze drying for scanning electron microscopy: a quantitative and qualitative study on isolated hepatocytes.

Critical-point drying and freeze drying were compared both quantitatively and qualitatively as preparative procedures for scanning electron microscopy. Isolated hepatocytes were used as model cells. Nomarski differential interference contrast microscopy was used for light microscopic measurements of the hepatocytes in the unfixed, the glutaraldehyde fixed, the glutaraldehyde + OsO4 fixed, the critical-point dried and the freeze dried states. Critical-point dried hepatocytes were found to shrink to 38% of glutaraldehyde + OsO4 fixed volume, whereas optimal freeze dried hepatocytes (frozen in water saturated with chloroform and freeze dried at 183 K for 84 h) were found to shrink to 51% of glutaraldehyde + OsO4 fixed volume. Transmission and scanning electron micrographs of the critical-point dried cells showed well-preserved ultrastructure and surface structure. Micrographs of the freeze dried cells showed ultrastructure destroyed by internal ice crystals and surface structure destroyed by external ice crystals. Double-fixed isolated hepatocytes were shown to swell during storage in buffer and to shrink during storage after critical-point drying. For low magnification scanning electron microscopy (up to about 3000 times) both critical-point drying and freeze drying can be used. However, for high magnification scanning electron microscopy, critical-point drying is superior to freeze drying.

Animals↗

PubMed1982

Effects of a small serosal hydrostatic pressure on sodium and water transport and morphology in rabbit gall-bladder.

1. In order to investigate the mechanism of serosal pressure-induced inhibition of isosmotic fluid transport, the effect of 4.5 cm water serosal pressure on spontaneous water transfer (J(v)) in rabbit gall-bladders was measured (in the presence of a supporting soft nylon net on the mucosal side) in a modified Ussing chamber. This allowed unidirectional Na(+) fluxes ([Formula: see text] and [Formula: see text]), transepithelial potential difference and resistance (R(t)) to be measured simultaneously. The effects of the serosal pressure were also investigated by light and electron microscopy.2. During pressure application, R(t) increased due to a covering effect of the mucosal support. The serosal pressure caused a parallel decrease in J(v) and net Na(+) transport ([Formula: see text]) across the free epithelial surface of 80-85%. About 85% of the decrease in [Formula: see text] was due to a decrease in [Formula: see text].3. After inhibition of 93% of fluid absorption by serosal 10(-3)M-ouabain, pressure-induced change in J(v) was only 8% of the spontaneous fluid transport rate.4. Control Na(+) flux ratio ([Formula: see text]) was 3.5. The pressure-induced increase in steady-state [Formula: see text] of 30-35% therefore contributed little to the decrease in [Formula: see text]. Further, this increase in [Formula: see text] was completely prevented by mucosal 10(-3) M-amiloride.5. All pressure-induced effects on transport and electrical parameters were reversible.6. The light microscopical and scanning electron microscopical results showed that half of the epithelial surface was covered by the nylon net following serosal pressure application. Ruptures in the epithelium were not seen. Thin section and freeze fracture electron microscopy demonstrated continuous, well developed tight junctions both in control and experimental condition.7. It is concluded that a serosal pressure of only 4.5 cm water causes inhibition of a cellular active Na(+) and water transport with only minimal, if any, contribution from paracellular filtration. This would seem incompatible with the concept that an active ion transport mechanism localized in the basolateral cell membrane is responsible for transepithelial fluid transport. The possibility of a mechanical fluid transport mechanism via elements of a tubulo-cisternal endoplasmic reticulum is raised.

Amiloride↗