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  • 1
    ISSN: 1432-0878
    Keywords: Na-K-ATPase ; Cell-membrane area ; Renal distal tubule ; Cortical collecting duct ; Mineralocorticoids ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Na-K-ATPase activity was measured in the convoluted part of the distal tubule (DCT), the connecting tubule (CNT) and the cortical collecting duct (CCD). The segments were microdissected from freeze-dried kidney tissue of rabbits adapted to various salt diets and exposed to large differences in endogenous and exogeneous mineralocorticoids. The Na-K-ATPase activity in the DCT is not influenced by mineralocorticoids. They do influence the activity in the CNT and in the CCD. In the CNT the highest activity was found with a low Na-, high K-diet. At the beginning of the CNT the enzyme activity is higher than in the end portion. While canrenoate-K treatment has no effect on Na-K-ATPase activity in the initial portions of the CNT, this drug decreases the Na-K-ATPase activity significantly in the end portion of the CNT. DOCA treatment has a significant effect on the enzyme activity in the CNT only in the end-portion of the segment, but provokes the highest Na-K-ATPase activity in the CCD. The changes in Na-K-ATPase are found to be associated with corresponding changes in the baso-lateral cell-membrane area in the segments affected.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0878
    Keywords: Kidney ; 5′-Nucleotidase ; Adenosine ; Interstitium ; Fibroblasts ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The hydrolysis of 5′-AMP by 5′-nucleotidase is the main source of adenosine. In various tissues adenosine is a local mediator adjusting the organ work to the available energy. In the kidney it regulates renal hemodynamics, glomerular filtration rate and renin release via specific receptors of the arteriolar walls. By immunocytochemistry we identified interstitial and tubular sites of 5′-nucleotidase in the rat kidney. In the interstitium the enzyme was detected only in the cortical labyrinth, the compartment that comprises all arteriolar vessels besides other putative targets of adenosine. The 5′-nucleotidase-positive cells of the interstitium were identified as fibroblasts. The fibroblasts are in close contact with the tubules as well as with the vessels. Thus, any 5′-AMP released by the tubules into the interstitial space would be converted to adenosine in the direct vicinity of its assumed targets. Adenosine produced by tubular cells would hardly have access to its known targets, since 5′-nucleotidase is restricted to the luminal cell surface. Pathological events affecting the fibroblasts might influence renal function by modifying the interstitial adenosine production.
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  • 3
    ISSN: 1432-0878
    Keywords: Renal distal tubule ; Cortical collecting duct ; Cell membrane area ; Mineralocorticoids ; K- and Na-adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The baso-lateral cell-membrane area in kidney tubules appears to be associated with the capacity for electrolyte transport; in the rabbit, it decreases from the distal convoluted tubule (DCT-cells) over the connecting tubule (CNT-cells) to the cortical collecting duct (principal cells). Adaptation to low Na-, high K-intake changes this pattern: CNT-cells at the beginning of the connecting tubule have the highest membrane area, which decreases along the segment, but remains two-fold higher than in controls. Principal cells have a four-fold higher membrane area than in controls. Simultaneous treatment with the antimineralocorticoid canrenoate-K inhibits the structural changes in CNT-cells only in end-portions of the connecting tubule and in principal cells. After prolonged high Na-, low K-intake DCT-cells display a two-fold higher membrane area than controls, while CNT-cells and principal cells are not affected. Simultaneous treatment with DOCA does not affect the DCT-cells but provokes a moderate increase in membrane area in CNT-cells, and a 5.5-fold increase in principal cells. The data provide evidence that DCT-, CNT- and principal cells are functionally different cell types. The baso-lateral cell-membrane area, associated with electrolyte-transport capacity, appears to be influenced in DCT-cells mainly by Na-intake, in CNT-cells mainly by K-intake and in part also by mineralocorticoids, and in principal cells mainly by mineralocorticoids.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0878
    Keywords: Antigen-presenting cells ; Major histocompatibility complex class II (MHC class II) ; Macrophages ; Dendritic cells ; Meninges ; Dorsal root ganglia ; Spihal cord ; Rat (Wistar, SIV, Brown-Norway: Ch. Rivcr Wiga)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract This report deals with the distribution, morphology and specific topical relationships of bone-marrow-derived cells (free cells) in the spinal meninges and dorsal root ganglia of the normal rat. The morphology of these cells has been studied by transmission and scanning electron microscopy. Cells expressing the major histocompatibility complex (MHC) class II gene product have been recognized by immunofluorescence. At the level of the transmission electron microscope, free cells are found in all layers of the meninges. Many of them display characteristic ultrastructural features of macrophages, whereas others show a highly vacuolated cytoplasm and are endowed with many processes. These elements lack a conspicuous lysosomal system and might represent dendritic cells. Scanning electron microscopy has revealed that free cells contact the cerebrospinal fluid via abundant cytoplasmic processes that cross the cell layers of the pia mater and of the arachnoid. Cells expressing the MHC class II antigen are also found in all layers of the meninges. They are particularly abundant in the layers immediately adjacent to the subarachnoid space, in the neighbourhood of dural vessels, along the spinal roots and in the dural funnels. In addition to the meninges, strong immunoreactivity for MHC class II antigen is observed in the dorsal root ganglia. The ultrastructural and immunohistochemical findings of this study suggest the existence of a well-developed system of immunological surveillance of the subarachnoid space and of the dorsal root ganglia.
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  • 5
    Publication Date: 1980-02-01
    Print ISSN: 0003-2697
    Electronic ISSN: 1096-0309
    Topics: Biology , Chemistry and Pharmacology
    Published by Elsevier
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  • 6
    Publication Date: 1981-05-18
    Print ISSN: 0014-5793
    Electronic ISSN: 1873-3468
    Topics: Biology , Chemistry and Pharmacology
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