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  • 1995-1999  (2)
  • Antigenität  (1)
  • Heat shock proteins  (1)
  • insulin secretion
  • 1
    ISSN: 1432-5233
    Keywords: Cytokine ; Islet of Langerhans ; Insulin secretion ; Nitrite ; Heat shock proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The influence of beta cell activity on cytokineinduced functional and structural impairments as well as the ability of those damaged cells to recover were investigated. Rat islets cultured for 4 days in the presence of 5, 10, and 30 mmol/l glucose were exposed to interferon-γ (IFN, 500 U/ml) and tumor necrosis factor-α (TNF, 250 U/ml) for the last 24 h. After cytokine removal islets were allowed to recover spontaneously in culture medium containing 10 mmol/l glucose for a further 7 days. Cytokines significantly inhibited insulin release into culture medium, insulin storage, glucose-stimulated insulin secretion, protein, and DNA synthesis. In the presence of cytokines there was a six- to eightfold increase in nitrite production by the islets. The functional impairments were more pronounced in metabolically stimulated beta cells. In addition, cytokines caused membrane alterations as indicated by increased spontaneous chromium-51 release. The cytokines specifically induced the synthesis of two proteins (72 and 88 kDa, respectively). By immunoblotting, the 72-kDa protein was identified as heat shock protein. After a 1-week recovery period, insulin storage and stimulated insulin secretion of cytokine-treated islets were still significantly diminished. However, protein and DNA synthesis of cytokine-exposed islets returned to pre-exposure levels. In conclusion, high beta cell activity increases islet susceptibility to TNF+IFN. Cytokine-induced, longlasting, inhibitory effects are primarily directed to betacell-specific functions, while general vital cell functions clearly recover after cytokine removal. The induction of certain proteins and the increased protein synthesis and replication rate after cytokine removal might reflect activated repair processes.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-3932
    Keywords: Schlüsselwörter Biokompatibilität ; Antigenität ; Polyester ; Kollagen ; Key words Biocompatibility ; Antigenicity ; Polyester ; Collagen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract At present there is neither an completely inert biomaterial available, nor does a universal test exist which objectively evaluates biocompatibility. One reason is the individuality of the host, especially with regard to the inflammatory response. Inflammation was found to induce biodegradation by hydrolysis or auto-oxidation of vascular prosthetic matrix after implantation. The present study was performed to investigate the specific humoral immune response after implantation of segments of a collagen-impregnated polyester prosthesis (Dacron) in Balb/c mice on experimental days 1, 18, 38, and 322. Serum antibody detection was performed by modified enzyme immunoassay using the prosthesis as a target. Specific polymer antibodies, enhanced by repeated implantations, could be detected in all mice which received grafts up to experimental day 322. These antibodies were not directed against the collagen coating. The antibody formation could be further enhanced by a combined administration of complete Freund's adjuvant together with the first implantation at experimental day 1. Results suggest that specific polymer antibodies, reflecting an inflammatory response, might be an additional parameter for biocompatibility testing of vascular prostheses.
    Notes: Zusammenfassung Bisher stehen keine komplett inerten Biomaterialien zur Verfügung und es existiert kein universeller Test zur Objektivierung der Biokompatibilität. Dies resultiert aus der individuellen Variabilität des Empfängerorganismus, insbesondere hinsichtlich der entzündlichen Reaktionsbereitschaft. Auch nach Implantation von Gefäßprothesen aus polymeren Biomaterialien kommt es zu einem chronischen Entzündungsprozeß. Dieser führt ursächlich durch Hydrolyse oder Autoxidation zur Biodegradation des Implantats. Mit unseren Untersuchungen galt es, eine möglicherweise bestehende, spezifische humorale Immunantwort nach Implantation von Segmenten einer kollagenimprägnierten Polyesterprothese (Dacron) in einem Tiermodell darzulegen. Balb/c-Mäusen wurde am 1., 18., 38. und 290. Versuchstag ein Prothesensegment intraperitoneal implantiert. Die Bestimmung der Serumantikörper erfolgte mit einem modifizierten Enzymimmunoassay unter Verwendung der Prothese als Target. Spezifische Antikörper gegen Polymere wurden nach wiederholter Implantation bei allen Tieren bis zum 322. Versuchstag nachgewiesen. Dabei konnte eine Antikörperbildung gegen die Kollagenimprägnierung ausgeschlossen werden. Die Antikörperbildung wurde durch den Zusatz von komplettem Freund-Adjuvans in Verbindung mit der ersten Implantation verstärkt. Der Nachweis von spezifischen Antikörpern gegen Polymere könnte zukünftig ein Parameter zur Testung der Biokompatibilität darstellen.
    Type of Medium: Electronic Resource
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