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Biomedical subjects

M Elger

Publications and source records attributed to M Elger.

46 records · Page 3Linked to original sources
PubMed1987

The branchial circulation and the gill epithelia in the Atlantic hagfish, Myxine glutinosa L.

The vessels of the branchial circulation of the Atlantic hagfish, Myxine glutinosa, and their relationship with the gill epithelia have been studied by light and electron microscopy. The inner surface of the pouch wall (containing the interconnected radial arteries) and the afferent and efferent unbranched portions (cavernous tissues) of the radially oriented gill folds are covered by a multilayered epithelium. The lamellar portion that is characterized by pillar cells is lined by a thin bilayered epithelium. The thin-walled sinusoid system is part of an arterio-venous circulation. This is demonstrated by the presence of arterio-venous anastomoses and by the connection to the peribranchial sinus. The sinusoid system has a close spatial relationship to the multilayered epithelium. The multilayered epithelium consists of pavement cells, cells of the medial layer and basal cells. Granulated cells are often found in the basal half of the epithelium. The pavement cells are characterized by large vesicles in close apposition to the apical plasma membrane. Ionocytes, which display a cytoplasmic tubular system that is continuous with the intercellular space, a high number of mitochondria, and small apical vesicles, are present. The occurence of the ionocytes in the afferent multilayered epithelium as well as the bilayered lamellar epithelium, the morphology of the ionocyte, and the absence of accessory cells is reminiscent of the freshwater teleost gill, and in part the elasmobranch gill, and is discussed in relation to osmo- and ion regulation.

Animals↗
PubMed1986

Chemical and morphological differences in the kidney zones of the elasmobranch, Raja erinacea mitch.

The histological investigation of the kidney of the skate Raja erinacea revealed a thin cap of dorsal bundles, which contain segments of single nephrons that are arranged separately in a countercurrent manner, and a large ventral zone, where the second proximal segments (PII) and parts of the lower nephron are located. This zonation is apparent in fresh, unfixed material and makes it possible to separate small tissue samples under a dissecting microscope. The osmolality in both zones does not differ. The dorsal bundle zone had a lower urea concentration and a higher sodium concentration than the ventral zone. The differences in the mean concentrations of the tissue samples indicate a gradient for the two substances along the bundles. Determinations of amounts of water and solutes per mg solute-free, dry tissue of the two zones, showed that the amounts of water, total osmolytes, Na and K were greater in the bundle zone than in the ventral zone, while the amount of urea was identical in the two zones. This indicates that the lower urea concentration in the bundle zone is established through an accumulation of Na and water in the interstitium. The countercurrent arrangement of very early and late segments of single renal tubules supports the concept of passive reabsorption of urea in the kidney of the marine elasmobranch.

Animals↗
PubMed1984

Ultrastructure and adrenergic innervation of preglomerular arterioles in the euryhaline teleost, Salmo gairdneri.

The opisthonephric kidney of the rainbow trout was investigated by light- and electron microscopy and a fluorescent-histochemical technique for biogenic amines was used. Preglomerular sphincters at the origin of afferent arterioles are present in this euryhaline teleost. The branching point of the afferent arteriole is characterized by (i) the formation of a right angle with the parent vessel, (ii) circularly arranged smooth muscle cells of the tunica media, (iii) additional circularly arranged smooth muscle cells intercalated between endothelium and tunica media, and (iv) a collar-like arrangement of several large endothelial cells with elaborate marginal folds and abundant myoendothelial junctions. A dense adrenergic innervation displaying specific fluorescence was found along the terminal arterioles and afferent arterioles, and conspicuously at the preglomerular sphincters. These results are suggestive of a neural participation in kidney function. They are discussed on the basis of recent evidence from pharmacological and physiological experiments for neural involvement in glomerular intermittency.

Animals↗
PubMed1981

The glomerulus of a stenohaline fresh-water teleost, Carassius auratus gibelio, adapted to saline water. A scanning and transmission electron-microscopic study.

Prussian carp, Carassius auratus gibelio, were maintained in aquaria with a salinity of 15 0/00 for 3 months. More than 90% of the glomeruli disappeared from the tissue as a result of the adaptation to saline water. Kidney tissue was excised and prepared for electron microscopy after perfusion fixation in situ. The fine structure of the renal corpuscle was compared with the normal ultrastructure of glomeruli of control fish from fresh-water aquaria. The main alterations include retraction of the endothelium from the basement membrane, widening of the subendothelial region, folding of the thickened basement membrane and epithelial layer, and the dislocation of slit diaphragms. The findings are discussed in relation to developmental stages of mammalian glomeruli and glomeruli from tissue cultures. The structural changes of the rudimentary glomeruli of the carp kept in 15 0/00 salt water differ from those observed in euryhaline fish from sea water.

Adaptation, Physiological↗
PubMedDate not supplied

Differences in rat kidney morphology between males, females and testosterone-treated females.

Kidneys of normal female and male Wistar-Kyoto rats were studied by standard morphological techniques and morphometry in order to evaluate possible differences in the overall kidney morphology between both sexes. Furthermore, we investigated the role of testosterone (DHT) on kidney morphology by treating females with daily DHT injections. Kidney weight and volume in relation to body weight were not significantly different between males and females and were not affected by DHT. Differences were found in the volume distribution among the kidney zones. The cortex was larger in males than in females, whereas the medulla was conspicuously larger in females than in males. The greater volume of the cortex in males was mainly due to a more extensive development of proximal tubules. DHT treatment in females increased the volume of their proximal tubules. Glomerular volume was similar among the three groups. Within the medulla, the difference was most prominent in the inner stripe (14.9% of the total kidney volume in females vs. 8.9% in males) and was also important in the inner medulla (7.0 vs. 4.8%). The absolute epithelial volume of thick ascending limbs in this zone was larger in females than in males. This difference was more pronounced in short loops (approximately 20%) than in long loops (approximately 10%). The values of the DHT-treated females ranged in between. In spite of the greater development of medulla and thick ascending limbs in females, urine concentration was higher in males than in females and maximum urinary concentrating ability after 48 h dehydration was not different between both sexes.

Animals↗