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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 174 (1986), S. 243-252 
    ISSN: 1432-0568
    Keywords: Amphibia Gymnophiona ; Kidney, Mesonephros ; Structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The structural organization of the kidney ofTyphlonectes compressicaudus (Amphibia, Gymnophiona) was studied by light microscopic (LM) examination of serial paraffin and semithin Epon sections. The kidney is slender and quite long and has a mesonephric segmental construction; the excretory duct (Wolffian duct), running along the lateral side of the kidney, segmentally receives the terminal trunks of the collecting duct system. The nephron has the following parts: renal corpuscle, neck segment, proximal tubule, intermediate segment, distal tubule and connecting tubule. The distal tubule is located in a ventromedial (central) zone of the kidney; all other tubular segments lie in a dorsolateral (peripheral) zone. The renal corpuscles are found at the border between these two zones. The renal corpuscle is very large; its urinary pole faces the peripheral zone. A small proportion of neck segments receive either a nephrostomal duct or a blind branch. The proximal tubule is a thick, highly convoluted tubule. The intermediate segment is ciliated and makes a few coils. The distal tubule is composed of three portions: a highly convoluted part in the central zone, subsequently an attachment site with the renal corpuscle and a short postattachment-part. The connecting tubule and the collecting duct have a heterogeneous epithelium consisting of light and dark cells. The collecting duct is distinguished by dilated intercellular spaces. The Wolffian duct has a pseudostratified epithelium. The present study correlates the course and segmentation of the renal tubule ofTyphlonectes. The tubule has three major convolutions. The first occurs in the proximal tubule in the peripheral zone; the second is established by the distal tubule and occurs in the central zone; the third is formed by the connecting tubule and is found in the peripheral zone.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 155 (1979), S. 149-160 
    ISSN: 1432-0568
    Keywords: Kidney ; Psammomys obesus ; Renal vasculature ; urine concentrating mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The vascular organization of the kidney of Psammomys obesus has been studied by injecting silicone rubber into the renal arterial and venous vessels and by standard histological techniques. Whereas the cortical vasculature is not principally different from that of other species, the medullary vessels show some unique features in the Psammomys. In the outer stripe, the vasa efferentia of juxtamedullary glomeruli give rise to primary vascular bundles which, in the transitional region between the outer and inner stripes, fuse to form secondary and, finally, giant vascular bundles. In the inner stripe exist two clearly separated vascular compartments that of the giant bundles and that of the interbundle region. The latter is supplied by arterial vasa recta originating from the upper part of the vascular bundles at the entrance to the inner stripe. In the lower portion, the separation of the two compartments is enhanced by vessel-free rims around the bundles (the rims contain descending, limbs of long loops only) and by protrusions of the renal pelvis. The inner zone is supplied exclusively by the vasa recta descending throughout the inner stripe within the vascular bundles. They splay out of the bundles at the transitions from outer to inner medulla, and descend individually as straight unbranched vessels. Many of them do not split up into capillaries before they reach the tip of the papilla. The venous drainage of the inner zone is ensured by venous vasa recta ascending individually up to the border between the inner zone and the inner stripe. They all enter the giant vascular bundles within which they traverse the inner stripe. The venous vessels draining the interbundle, region of the inner stripe do not join the bundles but ascend directly to the outer stripe. Thus, the circulations of the, outer and inner medullary zones are totally separated from each other. In the outer stripe venous vasa recta from the bundles and from the interbundle areas are mixed together. Most of them ascend high into the cortex within the medullary rays in close apposition to tubules, and empty into interlobular veins.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 170 (1984), S. 217-222 
    ISSN: 1432-0568
    Keywords: Juxtaglomerular apparatus ; Extraglomerular mesangial cell field ; Structure-function correlation ; Resetting of tubuloglomerular feedback ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The extraglomerular mesangial cell field was studied by morphometric techniques in volume expanded and volume depleted rats. The volume density of the extraglomerular mesangial interstitium was found to be significantly different between the two conditions, 16.9±3.7% in volume depletion and 29.0±4.1% in volume expansion. No difference in the volume density of the peritubular interstitium could be detected under the same conditions. These findings are interpreted as indicating a specific sensitivity of the extraglomerular mesangial interstitium to changes in body fluid content, a phenomenon which may play a role in the mechanism of resetting the tubulo-glomerular feedback control.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0568
    Keywords: Kidney ; Rabbit ; Juxtaglomerular apparatus ; Goormaghting cell ; Granular cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Goormaghtigh cells of the JGA are characterized by an extensive cellular ramification. In order to elucidate the shape and arrangement of the cell processes a three-dimensional model of a Goormaghtigh cell and of an adjacent granular cell has been constructed based on electron micrographs of a series of ultrathin sections. The model shows that a Goormaghtigh cell has the shape of a flatly pressed cylinder with both ends splitting up into a bunch of parallel processes. The processes maintain a close neighboring position and do not intermingle with processes of other Goormaghtigh cells. This feature is most puzzling when considering that Goormaghtigh cells and their processes are extensively connected by gap junctions. Even processes belonging to the same cell are electrically coupled with each other through gap junctions. The granular cells are clearly different in shape from Goormaghtigh cells. In granular cells bunches of processes are lacking. Granular cells obviously ramify into a few, large processes. The present findings are consistent with the assumption of a functionally central position of Goormaghtigh cells within the feedback mechanism of the JGA.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 176 (1987), S. 373-386 
    ISSN: 1432-0568
    Keywords: Renal glomerulus ; Mesangial cells ; Mesangial matrix ; Glomerular basement membrane ; Microfibrils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary It has been shown by many studies that mesangial cell contraction exerts considerable influences on glonerular filtration dynamics. However, experimental findings about the geometrical changes within the glomerular tuft going along with mesangial cell contractions are lacking. This study analyzes the geometry of mesangial cells and their relationship to glomerular capillaries, especially to the glomerular basement membrane (GBM). By applying a new staining technique of unosmicated specimens for TEM, the cellular outlines of glomerular cells (mesangial, endothelial and epithelial) and the distribution of extracellular matrices can be more easily studied than in conventionally osmicated specimens. It became obvious that mesangial cells and the GBM are extensively connected with each other, either by direct attachments or indirectly by microfibrils. These connections are especially prominent mesangial angles, i.e. at sites where the GBM deviates from its pericapillary course and covers the mesangium. Thereby, the GBM is not only coupled to the mesangium out—via mesangial cell processes—also to the GBM at the opposing mesangial angle. It seems possible that contraction of mesangial cells can bring the GBM from opposing mesangial angles closer together. Therefore we conclude that the GBM and the contractile mesangial cells together establish a biomechanical unit capable of developing wall tension in glomerular capillaries and of changing the geometry of glomerular capillaries following mesangial contraction or relaxation.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 177 (1988), S. 371-376 
    ISSN: 1432-0568
    Keywords: Intrarenal arteries ; Intrarenal veins ; Intraarterial cushions ; Renal blood flow ; SEM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The luminal aspect of intrarenal arteries and veins in the rat has been investigated by scanning electron microscopy (SEM). The endothelium of the intrarenal arteries consists of spindle-shaped cells and forms longitudinally running ridges which correlate with the folding pattern of the underlying internal elastic lamina. Intraarterial “cushions” were found at the origins of afferent arterioles from accuate arteries and along the entire course of interlobular arteries. The intrarenal veins are made up of a thin, extensively fenestrated epithelium equal to that of peritubular capillaries. The outer aspect of the endothelium contacts adjacent tubules as closely as the capillaries proper. Thereby, the luminal aspect of the veins exhibits a striking “tubule relief” created by the underlying tubules. This wall structure of the intrarenal veins suggest that diameter and shape of the veins are probably highly dependent on the surrounding interstitial pressure.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 175 (1987), S. 411-421 
    ISSN: 1432-0568
    Keywords: Plastination ; Preservation ; Macroscopy ; Technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This review surveys the potential of plastination, a technique of tissue preservation introduced eight years ago. In this process, water and lipids in biological tissues are replaced by curable polymer which are subsequently hardened, resulting in dry, odorless and durable specimens. The procedure consists of the following steps-fixation, dehydration, forced impregnation in a vacuum, and hardening. The properties of the finished specimen are determined by the class of polymer used. Silicone yields flexible, resilient speciemens, allows the broadest range of application, and provides satisfactory results with minimum equipment. Specimens plastinated with an epoxy-silicone copolymer are rigid enough to be polished, but are not unbreakable. This resin is used for thick, opaque body slices and showcase specimens. Epoxy resins are used for thin (2.5 mm), transparent body or organ slices. They are cast between polyester foils or glass plates and can be used for histological investigations. Polyester resin is used for the production of opaque brain slices, which gives excellent differentiation between grey and white matter. The application of plastination in research and the production of teaching specimens is discussed with special regard to the equipment required, cost, and feasibility of the processing.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 192 (1995), S. 385-397 
    ISSN: 1432-0568
    Keywords: Glomerular visceral epithelial cell ; Podocyte ; Structure-function relationship ; Cell culture ; Glomerular basement membrane ; Podocyte development ; Cell division
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Glomerular visceral epithelial cells, also termed podocytes, are highly specialized epithelial cells that cover the outer aspect of the glomerular basement membrane. Recent studies point to an important role of podocytes in the physiology and pathophysiology of the glomerulus. This review summarizes the structure-function relationships of podocytes. Following a description of the general morphology of podocytes, the technical problems associated with studying these cells are discussed. A survey of podocyte function forms the center of this review. Finally, selected aspects of podocyte development and cell division are discussed.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 60 (1982), S. 1063-1069 
    ISSN: 1432-1440
    Keywords: Renal medulla ; Circulation ; Blood vessels ; Nierenmark ; Blutgefäße ; Durchblutung
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die Gefäßversorgung des Nierenmarkes hat mehrere Besonderheiten. Die versorgenden Gefäße sind die efferenten Arteriolen der juxtamedullären Glomeruli. Die Blutversorgung ist damit postglomerulär. Die Verteilung des Blutes im Nierenmark geschieht durch die absteigenden Vasa recta, die in ihren Anfangsabschnitten noch Arteriolen sind. Zusammen mit aufsteigenden Vasa recta bilden sie die Gefäßbündel. Absteigende Vasa recta gehen auf jeder Ebene des Markes in Kapillaren über; die längsten verlaufen unverzweigt bis zur Papillenspitze. Die Kapillarplexus sind unterschiedlich entwickelt, einen dichten Kapillarplexus besitzt nur der Innenstreifen. In der Innenzone und im Außenstreifen übernehmen — zusätzlich zu den gering entwickelten Kapillaren — die aufsteigenden Vasa recta Kapillarfunktion. Die aufsteigenden Vasa recta führen das Blut aus dem Nierenmark ab. Sie entstehen auf jeder Ebene des Markes aus den Kapillaren und steigen als weitlumige, unverzweigte Gefäße bis zur Markrindengrenze auf; entsprechend ihrem Wandbau sind es Kapillaren. Vor ihrer Einmündung in die großen intrarenalen Venen durchqueren sie einzeln den Außenstreifen; aufgrund des hier gering entwickelten Interstitiums liegen sie den Tubuli sehr eng an. Dieses Arrangement wird im Hinblick auf pathologische Situationen der Niere als eine Schwachstelle der Nierenmarkdurchblutung interpretiert.
    Notes: Summary The blood vessels of the renal medulla have several particular features. The supplying vessels of the renal medulla are the efferent arterioles of the juxtamedullary glomeruli. Thus, the blood supply is entirely postglomerular. The distribution of the blood within the renal medulla is effected by the descending vasa recta. Descending and ascending vasa recta form the vascular bundles. Descending vasa recta leave the bundles at any level of the medulla to feed the adjacent capillaries; the longest descending vasa recta reach the papillary tip. The capillary plexus are differently developed. A dense capillary plexus is present only in the inner stripe of the outer medulla. In the inner medulla as well as in the outer stripe of the outer medulla the capillary plexuses are poorly developed. At these sites ascending vasa recta contribute to the capillarisation. The ascending vasa recta originate from capillaries at any level of the medulla and ascend without joining together towards the intrarenal veins at the cortico-medullary border. They are capillary vessels with wide lumina. Within the outer stripe of the outer medulla these vessels are very narrowly associated with the tubules; interstitial spaces are very poorly developed at this site. These relationships are interpreted as a possible weak point of the medullary circulation in pathological situations.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 394 (1982), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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