Biomedical subjects

K Qvortrup

Publications and source records attributed to K Qvortrup.

24 records · Page 2Linked to original sources

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↗

PubMed1991

Prostaglandin H synthase immunoreactivity in human gut. An immunohistochemical study.

Prostaglandins exhibit a variety of actions on intestinal smooth muscle depending upon the type, dose and muscle layer studied. As the cellular origin of prostaglandin H (PGH) synthase has not been established with certainty in the human gut wall, we studied the localization of PGH synthase in the human duodenum, jejunum, ileum and colon by immunohistochemistry. PGH synthase immunoreactivity appeared to be similar in all segments of the intestine. Most smooth muscle cells seemed to contain PGH synthase; however, the reaction in the lamina muscularis mucosae was much stronger than in the longitudinal and circular muscle layers. Endothelial cells in capillaries and larger vessels showed a positive reaction. In addition, unidentified cells in subserosa, at the level of Auerbach's plexus and in the submucosa were stained. We concluded that the smooth muscle cells of the human gut has a rather large capacity for PGH synthesis and the present results may provide a basis for a better understanding of both normal physiological functions as well as intestinal disease states involving disorders of prostaglandin synthesis.

Aged↗

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↗