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  • 1
    Electronic Resource
    Electronic Resource
    Cells and intercellular contacts in glomeruli and tubules of the frog kidney (1982)
    Springer
    Cell & tissue research 226 (1982), S. 589-608 
    Details
    ISSN: 1432-0878
    Keywords: Kidney (frog) ; Glomerulus ; Nephron ; Tight junctions ; Freeze-fracturing ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary By the use of thin sections and freeze-fracture replicas the glomerular and tubular structures of the kidney of the frog (Rana esculenta) were studied with special reference to intercellular junctions. In the glomerulus the filtration barrier is of very variable thickness, and frequent tight and gap junctional contacts occur between podocyte processes. Although structurally less elaborate, the proximal tubule resembles its mammalian counterpart. In the initial part the tight junctions are relatively shallow but become very broad in the mid and distal portions of the proximal tubule. The proximal tubular cells are extensively linked by gap junctions. In some animals the shapes of the cells in the proximal and distal portions of the proximal tubule were markedly different. The distal tubule consists of two segments which differ mainly in the pattern of interdigitations and the structure of the zonulae occludentes. Similarities with the tight junctional morphology of the mammalian distal tubule are striking. In the first part of the distal tubule (diluting segment) a narrow band of parallel tight junctions is found closely resembling that found in the mammalian straight distal tubule; in the more distal part of the distal tubule, however, a broad band of anastomosing tight junctional strands exists, like the zonula occludens of the mammalian convoluted distal tubule. The connecting tubule displays cellular dimorphism: its wall contains a mixture of light and dark (flask) cells. The luminal and basolateral membranes of the flask cells are covered with numerous rod-shaped particles. The tight junctions of the connecting tubule are broad and increase in depth and number of strands along its length; they are typical of a very tight epithelium. In spite of several dissimilarities with phylogenetically younger kidneys our findings suggest that many structural principles of the mammalian kidney are also represented in the kidneys of amphibians. The structural-functional relationships are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00214787
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Freeze-fracturing and deep-etching with the volatile cryoprotectant ethanol reveals true membrane surfaces of kidney structures (1980)
    Springer
    Cell & tissue research 210 (1980), S. 57-69 
    Details
    ISSN: 1432-0878
    Keywords: Freeze-fracturing ; Deep-etching ; Cryoprotectants ; Mammalian kidney ; Membrane surfaces ; Surface coat ; Tight junction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary With the conventional freeze-fracture technique applied to biological specimens, cell membranes split along an interior plane and two membrane faces are produced. True membrane surfaces remain hidden and can only be uncovered by deep-etching. To date, deep-etching could not be satisfactorily performed in the presence of cryoprotective agents since conventional cryoprotectants do not sublime due to their low vapour pressure. This lack of suitable volatile cryoprotectants has limited deep-etching so far to very small objects which can be cryofixed without cryoprotectants. As a consequence, our freeze-fracture knowledge of cell surfaces is still poor. The present study shows that ethanol is a suitable volatile cryoprotectant for the freeze-fracture technique, and provides a novel approach to the routine deep-etching of freeze-fracture specimens without the need for special equipment. With ethanol deep-etching, true outer cell-surfaces are demonstrated within the kidneys of rat and Psammomys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232141
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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