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  • 1
    ISSN: 1438-2199
    Keywords: Amino acids ; Non-proteinogenic optically active amino acids ; D- and L-enantiomers ; Dehydroamino acids ; Chiral rhodium catalysts ; Asymmetric hydrogenation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Non-proteinogenic amino acids play an increasing role in oligopeptide chemistry. Their pharmacological and chemical properties, caused by D-configuration and “unnatural” residues, are more and more used for drug design. Different methods of asymmetric synthesis have been developed during the last decade to prepare “unusual” amino acids. One of them, the asymmetric hydrogenation of dehydroamino aids catalyzed by chiral rhodium (I) complexes, will be described. A series of examples, D- and L-configured, like naphthyl-, thienyl-, furyl-, and pyridylalanines, as well as phenylalanines substituted by chlorine, fluorine, p-nitro, p-methyl, p-trifluoromethyl, p-isopropyl, and p-tert-butyl have been prepared and characterized. Some analytical data like melting points and values of optical rotation are summarized in tables.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1435-2451
    Keywords: Lebertransplantation ; Warme Ischämie ; Organkonservierung ; Kalte Konservierung ; Normotherme Perfusion ; Reperfusion ; Liver transplantation ; Warm ischemia ; Organ preservation ; Cold storage ; Normothermic perfusion ; Reperfusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Warm ischemia is known to induce substantial damage to the liver parenchyma. With respect to clinical liver transplantation, the tolerance of the liver to warm ischemia and the preservation of these organs have not been studied in detail. In isolated reperfused pig livers we proceeded according to the following concept: Livers were subjected to 1 or 3 h of warm ischemia. Subsequently, these organs were preserved by either normothermic perfusion or cold storage (histidine-tryptophan-α-ketoglutarate, HTK) for 3 h each. After storage, liver function was assessed in a reperfusion circuit for another 3 h. Parameters under evaluation were bile flow, perfusion flow, oxygen consumption, enzyme release into the perfusate (creatine kinase, glutamic oxaloacetic transaminase (GOT), lactic dehydrogenase, and glutamic pyruvic transaminase), and histomorphology. Damage to the liver was lowest after warm ischemia of 1 h. The results after cold storage were superior to those after normothermic perfusion (GOT: 3.2±0.3 and 2.6±0.2 U/g liver; cumulative bile production: 14.7±2.1 and 9.4±1 ml, respectively;P〈0.05). In contrast, we found substantial damage at the end of reperfusion in livers undergoing 3 h of warm ischemia under both preservation techniques with severe hepatocellular pyknoses and essentially altered nonparenchymal cells. The results suggest that pig livers undergoing 1 h of warm ischemia and cold storage for 3 h with HTK solution may lead to functioning after transplantation.
    Notes: Zusammenfassung Die Verwendung von Lebern mit einer Vorschädigung durch warme Ischämie zur Transplantation wird kontrovers diskutiert. Im Modell der isoliert reperfundierten Schweineleber wurden nach vorausgegangener warmer Ischämie von 1 oder 3 h die Konservierungskonzepte „kalte Konservierung mit HTK-Lösung (Histidin-Tryptophan-α-Ketoglutarat)“ und „normotherme Perfusion“ für jeweils 3 h verglichen. Während einer 3 stündigen Reperfusion wurden neben einer lichtmikroskopischen Auswertung Gallefluß, Perfusionsfluß, Sauerstoffverbrauch und Enzymfreisetzung (Creatin-Kinase, Glutamat-Oxalacetat-Transaminase, Glutamat-Pyruvat-Transaminase und Laktat-Dehydrogenase) gemessen. Nach 1 stündiger warmer Ischämie führte die kalte Konservierung im Vergleich zur normothermen Perfusion zu einer geringeren Schädigung (GOT: 3,2±0,3 und 2,6±0,2 U/g Leber; Gesamtgallefluß: 14,7±2,1 und 9,4±1 ml;P〈0,05). Nach einer warmen Ischämie von 3 h waren bei beiden Konservierungsverfahren die Veränderungen erheblich. Die lichtmikroskopische Untersuchung zeigte Pyknosen von Hepatozyten und sinusoidalen Zellen mit teilweiser Auslösung aus dem Zellverband. Die Ergebnisse belegen, daß im Modell der isoliert reperfundierten Schweineleber eine warme Ischämie von 1 h toleriert wird. Für die Konservierung dieser vorgeschädigten Organe kann das Konzept der hypothermen Konservierung mit HTK-Lösung für einen Zeitraum bis zu 3 h empfohlen werden.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1435-2451
    Keywords: Schlüsselwörter Lebertransplantation ; Warme Ischämie ; Organkonservierung ; Kalte Konservierung ; Normotherme Perfusion ; Reperfusion ; Key words Liver transplantation ; Warm ischemia ; Organ preservation ; Cold storage ; Normothermic perfusion ; Reperfusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Warm ischemia is known to induce substantial damage to the liver parenchyma. With respect to clinical liver transplantation, the tolerance of the liver to warm ischemia and the preservation of these organs have not been studied in detail. In isolated reperfused pig livers we proceeded according to the following concept: Livers were subjected to 1 or 3 h of warm ischemia. Subsequently, these organs were preserved by either normothermic perfusion or cold storage (histidine-tryptophan-α-ketoglutarate, HTK) for 3 h each. After storage, liver function was assessed in a reperfusion circuit for another 3 h. Parameters under evaluation were bile flow, perfusion flow, oxygen consumption, enzyme release into the perfusate (creatine kinase, glutamic oxaloacetic transaminase (GOT), lactic dehydrogenase, and glutamic pyruvic transaminase), and histomorphology. Damage to the liver was lowest after warm ischemia of 1 h. The results after cold storage were superior to those after normothermic perfusion (GOT: 3.2±0.3 and 2.6±0.2 U/g liver; cumulative bile production: 14.7±2.1 and 9.4±1 ml, respectively; P〈0.05). In contrast, we found substantial damage at the end of reperfusion in livers undergoing 3 h of warm ischemia under both preservation techniques with severe hepatocellular pyknoses and essentially altered nonparenchymal cells. The results suggest that pig livers undergoing 1 h of warm ischemia and cold storage for 3 h with HTK solution may lead to functioning after transplantation.
    Notes: Zusammenfassung Die Verwendung von Lebern mit einer Vorschädigung durch warme Ischämie zur Transplantation wird kontrovers diskutiert. Im Modell der isoliert reperfundierten Schweineleber wurden nach vorausgegangener warmer Ischämie von 1 oder 3 h die Konservierungskonzepte ,,kalte Konservierung mit HTK-Lösung (Histidin-Tryptophan-α-Ketoglutarat)`` und ,,normotherme Perfusion`` für jeweils 3 h verglichen. Während einer 3 stündigen Reperfusion wurden neben einer lichtmikroskopischen Auswertung Gallefluß, Perfusionsfluß, Sauerstoffverbrauch und Enzymfreisetzung (Creatin-Kinase, Glutamat-Oxalacetat-Transaminase, Glutamat-Pyruvat-Transaminase und Laktat-Dehydrogenase) gemessen. Nach 1 stündiger warmer Ischämie führte die kalte Konservierung im Vergleich zur normothermen Perfusion zu einer geringeren Schädigung (GOT: 3,2±0,3 und 2,6±0,2 U/g Leber; Gesamtgallefluß: 14,7±2,1 und 9,4±1 ml; P〈0,05). Nach einer warmen Ischämie von 3 h waren bei beiden Konservierungsverfahren die Veränderungen erheblich. Die lichtmikroskopische Untersuchung zeigte Pyknosen von Hepatozyten und sinusoidalen Zellen mit teilweiser Auslösung aus dem Zellverband. Die Ergebnisse belegen, daß im Modell der isoliert reperfundierten Schweineleber eine warme Ischämie von 1 h toleriert wird. Für die Konservierung dieser vorgeschädigten Organe kann das Konzept der hypothermen Konservierung mit HTK-Lösung für einen Zeitraum bis zu 3 h empfohlen werden.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0899-0042
    Keywords: amino acids ; chiral rhodium complexes ; aminophosphine-phosphinite ; D- and L-enantiomers ; NMR spectra ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Substituted N-Cbz and N-Boc protected arylamino acrylic acids and esters have been prepared and used in asymmetric hydrogenations catalyzed by PROPRAPHOSRh. Stereoselectivities 〉 90% ee could be achieved, the rate of which is dependent on the position of the substituent in the aromatic ring. The N-Boc derivatives provide advantages compared with the N-Cbz analogues. The amino acid derivatives were fully characterized by 19F, 13C, and 1H NMR spectroscopy. © 1996 Wiley-Liss, Inc.
    Additional Material: 12 Tab.
    Type of Medium: Electronic Resource
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