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  • Electronic Resource  (3)
  • cognate peptide substrate  (2)
  • Angiotensin II  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Zur Reagibilität des Renin-Angiotensin-Systems bei kardialer Hydropsie: Hinweise auf eine vom Gesamtnatriumbestand abhängige Regulation der Reninfreisetzung (1972)
    Springer
    Journal of molecular medicine 50 (1972), S. 311-326 
    Details
    ISSN: 1432-1440
    Keywords: Plasma renin activity ; Angiotensin II ; Cardiac edema ; Furosemide ; Regulation of sodium balance ; Plasma-Renin-Aktivität ; Angiotensin II ; kardiale Hydropsie ; Furosemid ; Regulation des Naturiumhaushaltes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung An 8 Gesunden und 21 Kranken mit kardialer Insuffizienz wurden Renin-Aktivität (PRA) und Angiotensin II-Konzentration (A II) im Plasma, Serumnatrium und -kalium und renale Na+-, K+- und Flüssigkeitsexkretion vor sowie 2, 4 und 6 Std nach i.v. Gabe von 0,3 mg Furosemid/kg untersucht. Die PRA wurde biologisch, A II radioimmunologisch bestimmt. Die Gesunden reagierten mit signifikanten Anstiegen der PRA- und A II-Werte (P〈0,005), die Kranken mit kardialer Insuffizienz zeigten 3 verschiedene Verhaltensmuster der PRA: Absinken unter den Ruhewert (4 Fälle), Anstieg (4 Fälle) und Gleichbleiben (14 Fälle, davon 11 ohne meßbare PRA). Eine mangelhafte Stimulierbarkeit der PRA ist somit auch bei kardialer Hydropsie möglich. Die Pat. mit abfallender bzw. gleichbleibender PRA waren vornehmlich Schwerkranke mit ausgeprägter Hydropsie; sie wiesen nach Furosemid im Mittel gleich große, im einzelnen z.T. weit höhere Na+-Verluste auf als die Gesunden. Dies könnte durch die Annahme eines (zentralnervösen) Systems erklärt werden, das die renale Na+-Verlustrate in Beziehung zum Na+-Gesamtbestand setzt und erst ab einer kritischen Relation gegenregulatorisch die Steigerung der Reninfreisetzung veranlaßt. Diese Vermutung wurde durch Untersuchung einer Patientin vor und nach Ödemausschwemmung wahrscheinlich gemacht. PRA- und A II-Werte verhielten sich konkordant (r=+0,627,P〈0,001).
    Notes: Summary In 21 patients with congestive heart failure and 8 normal controls plasma renin activity (PRA), angiotensin II (A II), sodium and potassium concentrations in plasma and renal Na+, K+, and water excretion were measured before and 2, 4, and 6 hours after an intravenous injection of Furosemide (0.3 mg/kg). PRA was determined biologically, A II by radioimmunoassay. The control group showed a significant increase of PRA and A II levels (P〈0.005). In patients with congestive heart failure, three different patterns of PRA were observed: decrease (4 cases), increase (4 cases) and no change (14 cases which comprise 11 patients without detectable PRA), compared to the individual control value. Thus, inadequate stimulation of PRA may occur in congestive heart failure, too. Particularly the patients with decreasing or unchanged PRA suffered from severe cardiac insufficiency with severe edema. After application of Furosemide, these patients showed in average the same, some of them a much higher Na+ loss than the controls. These results could be explained by the assumption of the presence of a control mechanism, possibly located in the brain, that detects the renal Na+ excretion in relation to the total body Na+ and induces the counterregulatory renin secretion not unless a certain reference value is attained. This hypothesis was supported by the results obtained in the same patient before and after loss of edema. PRA and A II values were concordant (r=+0.627,P〈0.001).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01485179
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  • 2
    Electronic Resource
    Electronic Resource
    Development of a sensitive peptidase assay: In search of cell associated proteases responsible for the cleavage of prepro TGFα (1992)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 48 (1992), S. 411-423 
    Details
    ISSN: 0730-2312
    Keywords: cognate peptide substrate ; preprotein processing ; prepro TGFα ; HeLa cells ; cell surface proteases ; aminopeptidases ; endopeptidases ; product profiling ; thin layer chromatography ; factor regulation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A radiometric assay has been developed for the detection of proteolytic activity capable of releasing transforming growth factor alpha (TGFα) from its membrane bound precursor. The assay is dependent upon the separation by thin layer chromatography of hydrolytic products of a nonapeptide substrate containing a radioactive iodinated tyrosine residue as a reporting group N-terminal to an octapeptide which is cognate to the N-terminal cleavage sequence of TGFα. We describe the selectivity of the peptidase assay with commercially purified proteases and with cell-associated peptidases, its exquisite sensitivity, and its applicability to defining peptidase activity, which may be responsible for the processing of the membrane-bound prepro TGFα. The activity of two different elastases had different profiles which thus may be of use in characterizing them. The characteristics of the intact and extracted HeLa cell assay with respect to time, cell density, and peptidase concentration are defined, as are conditions needed to remove endogenous, confounding, proteolytic activity from the serum used to support cell culture. Intact HeLa cell cultures exhibit both exo- and endo-peptidase activity at approximately equal levels in both sparse and dense monolayer culture without relationship to cell density, and at a level equal to 1-2% of total cell activity of these enzyme classes.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240480410
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  • 3
    Electronic Resource
    Electronic Resource
    Low fluences of ultraviolet irradiation stimulate hela cell surface aminopeptidase and candidate “TGFαase” activity (1993)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 51 (1993), S. 102-115 
    Details
    ISSN: 0730-2312
    Keywords: cognate peptide substrate ; post-translational stimulation ; cycloheximide activation ; preproTGFα ; bestatin ; ectopeptidases ; ultraviolet irradiation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Several forms of perturbation result in the release of bioactive molecules into the microenvironment of injured cells to mediate the inflammatory or reparative reactions which restore normal tissue structure and function. Amongst other products, ultraviolet irradiation (UV) causes the release of the growth factor TGFα from a variety of epithelial cell sources, apparently by a post-translational mechanism. Here we have explored the hypothesis that UV results in the activation of cell surface proteases which may then be capable of excising mature TGFα from its plasma membrane-bound precursor. Using a recently described, sensitive assay of peptidase activity tailored to the substrate requirements for cleavage of the scissile bonds in proTGFα, we have found that nonlethal fluences of UV ( 〈 12 Jm-2) to HeLa cell cultures are followed by large increases in cell surface proteolytic activities. Amongst these, endopeptidase activity produces a similar product profile from the nonapeptide substrate to that of human leukocyte elastase, an enzyme previously shown to be capable of releasing a bioactive, mature form of TGFα from its cell-bound precursor. However, in addition to this candidate “TGFase” activity, cell surface aminopeptidase activity was also very significantly increased. The increase in the two classes of peptidase function differed in the timing of their responses. Aminopeptidase activation occurred immediately following UV, peaking after some 15-20 h, whereas the increase in endopeptidase activity lagged 6 h behind, cresting after 20-24 h. No evidence for a role for aminopeptidase in the activation of the endopeptidase could be found. Also, there was no increase in the total proteolytic activity demonstratable in cell extracts following UV.Attempts to interrupt the UV peptidase activation by inhibiting protein synthesis with cycloheximide were unsuccessful; rather, the inhibitor itself caused an increase in both classes of peptidase activity during the first 20 h. Unlike the UV response, both the aminopeptidase and endopeptidase ectoactivities increased simultaneously within a few hours of introducing cycloheximide into the medium of unirradiated cultures. The cycloheximide induced activity peaked after 20 h. Interestingly, cycloheximide alone has previously been shown to potentiate TGFα release from a cell line producing its precursor constitutively.These data suggest that both UV and cycloheximide can initiate reactions in HeLa cells which result in ectopeptidase activation of a global nature. Since both agents result in rapid interruption of DNA synthesis, it is possible that this cell surface proteolytic response may be analogous to, or part of, the “mammalian genetic stress response.” The mechanism of the activation of the cell surface proteases appears to be post-translational, perhaps part of a proteolytic cascade originating from perturbed macromolecular synthesis. © 1993 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240510117
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