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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 43 (1965), S. 410-413 
    ISSN: 1432-1440
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary In micropuncture experiments of the rat kidney solutions of various electrolyte compositions were injected into the tubule near the site of the macula densa cells. In kidneys with high renin an increase in Na+-concentration at this site by injection of 150 mMol/l NaCl or NaBr produced a transient collapse of the proximal convolution only of the same nephron. The collapse occurred within 10 sec after injection and the tubule was completely reopened within 60 sec after injection was stopped. The reaction was often repeated in the tubule 20 times. 150 mMol/l cholinchloride and 300 mMol/l Mannitol injections were not followed by collapse. This indicates that the osmolar concentrationper se is not the primary cause of the reaction. The Na+-specific reaction was absent or almost abolished in renin depleted kidneys. The macula densa cells are part of the juxtaglomerular apparatus and in direct contact with the renin producing cells of the afferent arteriole of the same nephron. We would like to suggest that the proximal collapse is the result of constriction of the afferent arteriole due to stimulation of renin secretion by increased Na+-concentration at the macula densa site. This inverse relation between [Na+] at the macula densa site and glomerular filtration would in effect be a feedback mechanism for the regulation of tubular sodium load, GFR, and RBF.
    Notes: Zusammenfassung In Mikropunktionsversuchen an der Ratte wurde die Elektrolytzusammensetzung am Macula densa-Segment eines einzelnen Nephrons experimentell verändert. In Nieren mit hohem Reningehalt ließ sich durch Erhöhung der NaCl-Konzentration eine vorübergehende Unterbrechung des Glomerulumfiltrates dieses einzelnen Nephrons hervorrufen. Eine gleiche Wirkung hat NaBr, dagegen sind Cholinchlorid und elektrolytfreie Mannitollösung ohne Effekt. Diese Na+-spezifische Reaktion ist an stark reninverarmten Nieren nicht oder nur in geringem Ausmaß nachweisbar. Die Verminderung des Einzelnephronfiltrates setzt innerhalb von 10 sec nach Erhöhung der Na+-Konzentration im Macula densa-Segment ein. Das Macula densa-Segment steht als Bestandteil des juxtaglomerulären Apparates in direktem Kontakt mit den reninbildenden Epitheloidzellen der afferenten Arteriole der gleichen Nephroneinheit. Es ist naheliegend anzunehmen, daß die Filtratunterbrechung durch eine präglomeruläre Vasoconstriction, ausgelöst durch eine lokale Aktivierung des Renin-Angiotensin-systems, zustande kommt. Auf Grund unserer Befunde wird zwischen dem Macula densa-Segment und der afferenten Arteriole ein intrarenaler Rückkoppelungs-mechanismus zur Regulation des tubulären Na+-Loads postuliert, an dem das Renin-Angiotensinsystem beteiligt ist.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 52 (1974), S. 654-656 
    ISSN: 1432-1440
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 52 (1974), S. 703-704 
    ISSN: 1432-1440
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 55 (1977), S. 1177-1178 
    ISSN: 1432-1440
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 57 (1979), S. 993-999 
    ISSN: 1432-1440
    Keywords: Electron microprobe analysis ; Intracellular electrolytes ; Kidney ; Ischaemia ; Elektronenstrahl-Mikroanalyse ; Intrazelluläre Elektrolyte ; Niere ; Ischämie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to be able to examine the processes involved in transepithelial transport in tissues, which are not composed of a single cell type, methods are required, which permit analysis at a cellular level. The technique of electron microprobe analysis permits the intracellular concentrations of many elements to be determined simultaneously in various portions of the cell. The application of this method to renal cortical tissue has shown that the best estimates of the cytoplasmic concentrations are to be obtained in regions close to the nucleus, farthest from the basolateral infoldings and microvilli, which separate the intracellular environment from the extracellular space. The nuclear concentrations of Na and K do not differ from those in the surrounding cytoplasm, although those of P and C1 are somewhat higher in cytoplasm. The intracellular element concentrations in the different cell types vary somewhat, proximal tubular cells contain higher concentrations of Na and C1 and lower ones of P than distal tubular cells. Following ischaemia, a manoeuvre know to result in a disturbance of intracellular electrolytes, Na was observed to rise and K to fall only in the non-surface cells of kidneys exposed to the air, but in all cells, if the kidneys were kept air-free in an atmosphere of N2. The proximal and distal tubular cells showed a variable resistance to ischaemia, the distal tubular cells being much more resistant. Despite the severity of the electrolyte disturbance following ischaemia, the intracellular composition was completely restored one hour after re-introducing renal blood flow.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1424
    Keywords: exocrine glands ; ion secretion ; electron microprobe analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary In the intact, in vitro frog skin, isoproterenol (ISO) stimulates and amiloride-insensitive increase in short-circuit current (SCC) that can be localized to the exocrine glands and is associated with secretion of chloride. To determine which cells in the glands respond to stimulation we measured the intracellular electrolyte concentrations of the various cell types of the mucous and seromucous glands of the skin using freeze-dried cryosections and electron microprobe analysis. In the resting state, the various cell types of the glands have intracellular electrolyte concentrations similar to the epithelial cells of the skin. Exposure to amiloride (10−4 m) has little effect on the concentration of Na and Cl in the cells of the glands. The effect of isoproterenol has two distinct phases. Analysis of glands in tissues frozen at the peak of the SCC response (13 min after addition of isoproterenol) shows that the only significant change is an increase in Na and Ca in a group of cells at the ductal pole of the acini of both gland types. These are termed “gland” cells. The duct cells and cells that secrete macromolecules did not show any significant changes at this timepoint. In the gland cells, after a one-hour exposure to isoproterenol the Na concentration is at prestimulation levels while Cl drops. There is also a smaller drop in Cl in the duct and skin epithelial cells. Ouabain, which can completely block the isoproterenol SCC response, has little short-term effect on Na and Cl in the control gland but accentuates the gain of Na and drop in Cl in the isoproterenol-treated condition. Bumetanide and, to a lesser extent, furosemide, also blocks the isoproterenol SCC response and causes a further drop in Cl. The results provide indirect evidence that a major portion of the ionic component of the gland secretion is produced by a distinct group of cells separate from those producing the macromolecular component and that the mechanism of secretion involves a Na:Cl coupled transport system linked to the activity of the basolateral Na pump.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Cryobiology 11 (1974), S. 563 
    ISSN: 0011-2240
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Physiology 30 (1968), S. 441-524 
    ISSN: 0066-4278
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Medicine , Biology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Comparative Biochemistry and Physiology -- Part A: Physiology 107 (1994), S. 57-61 
    ISSN: 0300-9629
    Keywords: Arginine vasopressin ; Glomerular nitration ; Propranolol ; Rehydrated Bedouin goats ; Renal function ; Renal plasma flow ; Urine flow
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Langenbeck's archives of surgery 304 (1963), S. 768-772 
    ISSN: 1435-2451
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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