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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 64 (1986), S. 829-837 
    ISSN: 1432-1440
    Keywords: Renin ; Renin activation ; Renin secretion ; Juxtaglomerular epithelioid cells ; Lysosomes ; Renin ; Reninaktivierung ; Reninsekretion ; Juxtaglomeruläre epithelioide Zellen ; Lysosomen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Der Artikel enthält einen Überblick über Aspekte der Reninsynthese und -sekretion, die im Vergleich zu den Verhältnissen bei anderen Systemen überwiegend atypisch sind. So besitzen die reninproduzierenden epithelioiden Zellen die Fähigkeit zur reversiblen metaplastischen Transformation in glatte Gefäßmuskelzellen, ihre Sekretgranula weisen einen sehr nahen Verwandtschaftsgrad zu Lysosomen auf, und die Zellen reagieren insofern in paradoxer Weise auf einen Anstieg des intracellulären freien Ca++, als die Reninsekretion dadurch gehemmt statt gesteigert wird. Schließlich wird der Modus der Reninsekretion im Zusammenhang mit der Reninaktivierung sowie möglichen Mechanismen zur Feineinstellung des Verhältnisses von sezerniertem aktivem zu inaktivem Renin in Abhängigkeit von den jeweiligen Erfordernissen des Renin-Angiotensin Systems diskutiert.
    Notes: Summary A survey is given about features of renin synthesis and secretion from juxtaglomerular epithelioid cells that are largely atypical as compared to those of other secretory systems. Renin-producing cells have the capability of reversible metaplastic transformation into vascular smooth muscle cells, their secretory granules are very closely related to lysosomes, and they react paradoxically, i.e. with an inhibition instead of a stimulation of renin secretion, to a rise in intracellular free Ca++. The modes of renin secretion and activation of the enzyme as well as possible mechanisms involved in adjusting the ratio of secreted active to inactive renin to the current needs of the renin-angiotensin system are discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 252 (1988), S. 687-690 
    ISSN: 1432-0878
    Keywords: Renin secretion ; Ca-dependence ; Vascular smooth muscle cells ; Afferent arteriole ; Myosin fibers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Most renin-positive cells of the preglomerular arteriole are intermediate in morphological appearence between smooth muscle cells and epithelioid cells. Intermediate cells contain, in addition to secretory granules, contractile proteins arranged as a sublemmal network. The paradoxical (inhibitory) role of calcium in renin secretion is explained, on the basis of these findings, by an increased tone of the sublemmal network; this might impair the preexocytotic access of renin granules to the cell membrane.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 131 (1986), S. 244-246 
    ISSN: 1615-6102
    Keywords: Calcium ion distribution ; Polar growth ; Pollen tube ; Quin-2 fluorescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using the fluorescent calcium probe Quin-2, we could demonstrate a tip-to-base gradient of free calcium within growing pollen tubes ofLilium longiflorum. This result shows that it is possible to visualize calcium ions using Quin-2 in plant cells which are surrounded by a cell wall and that the calcium gradients demonstrated by CTC fluorescence (indicating membrane-bound calcium) and PIXE (showing total calcium) is paralleled by a gradient of free calcium in pollen tubes.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1615-6102
    Keywords: Lilium ; Pollen tube ; Calcium gradient ; Polarity ; Protoninduced X-ray emission (PIXE) ; The Heidelberg proton microprobe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The intracellular calcium distribution in pollen tubes ofLilium longiflorum was measured by proton-induced X-ray emission (PIXE) with the Heidelberg proton microprobe, which is a new method for biological application. Studies by electron-induced X-ray emission (EIXE) were done in comparison. Independent of the preparation technique, the pollen tubes show a tip-to-base calcium gradient. The shape of the calcium gradient and the total calcium content depend on the preparation technique. The calcium ionophore A-23187 destroys the calcium gradient and leads to a loss of most cell calcium. Chlorotetracycline (CTC) treatment increases the amount of membrane-bound calcium.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1615-6102
    Keywords: Lilium ; Pollen tube ; Proton-induced X-ray emission (PIXE) ; The Heidelberg proton microprobe ; Polar zinc distribution ; mRNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The zinc distribution in pollen tubes ofLilium longiflorum was analysed by proton-induced X-ray emission (PIXE) with the Heidelberg proton microprobe. A very high zinc concentration was measured in the pollen tube tip region.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 139 (1987), S. 20-24 
    ISSN: 1615-6102
    Keywords: Calcium activity ; Calcium gradient ; Lilium ; Polar growth ; Pollen tube ; Quin-2 ; Microfluorimeter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Pollen tubes ofLilium longiflorum were loaded with quin-2 to determine the cytoplasmic free calcium. Quin-2-fluorescence was detected at 500 nm with alternating excitation at 340 nm and 360 nm. The calcium2+-concentration was obtained using the intensity ratio R=I340/I360. The analysis exhibits a [Ca2+] of nearly 10−7mol·l−1 in the tip region and about 2·10−8 mol·l−1at the tube base, near the pollen grain. The data give evidence for the existence of a continuous gradient of free calcium within growing pollen tubes of various length.
    Type of Medium: Electronic Resource
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