TY - CHAP A1 - Lohse, M. J. A1 - Klotz, K.-N. A1 - Schwabe, U. A1 - Christalli, G. A1 - Vittori, S. A1 - Grifantini, M. T1 - Pharmacology and Biochemistry of Adenosine Receptors N2 - Adenosine modulates a variety of physiological functions via membrane-bound receptors. These receptors couple via G proteins to adenylate cyclase and K+channels. The A1 subtype mediates an inhibition of adenylate cyclase and an opening of K+-channels, and the A2 subtype a Stimulation of adenylate cyclase. Both subtypes have been characterized by radioligand binding. This has facilitated the development of agonists and antagonists with more than 1000-fold A1 selectivity. A1-selective photoaffinity labels have been used for the biochemical characterization of A1 receptors and the study of their coupling to adenylate cyclase. Such selective ligands allow the analysis of the involvement of adenosine receptors in physiological functions. Selective interference with adenosine receptors provides new pharmacological tools and eventually new therapeutic approaches to a number of pathophysiological states. KW - Adenosinrezeptor KW - Pharmakologie KW - Toxikologie Y1 - 1988 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-86251 ER - TY - CHAP A1 - Shephard, S. E. A1 - Hegi, M. E. A1 - Lutz, Werner K. T1 - In-vitro assays to detect alkylating and mutagenic activities of dietary components nitrosated in situ N2 - Nitrosation of dietary components has been combined with the 4-(para-nitrobenzyl)pyridine (NBP) colorimetric test for screening alkylating agents and with the Ames test for the detection of mutagenic activity. This allowed the investigation of short-hved nitrosation products of dietary components which generate electrophilic degradation products requiring no metabolic activation (natural amino acids and some derivatives, ureas, guanidines, primary alkyl and aryl amines). In a first system, precursor, nitrous acid and NBP were present simultaneously. All amino acids tested, except glutamic acid and glutamine, gave positive results. The reactivities spanned more than three orders of magnitude, with the aromatic amino acids and methionine the most active; two primary amines, tryptamine and histamine, were also strongly reactive. All guanidines tested, except the amino acid arginine, gave negative results. A second system consisted of two phases: NBP was added only after destruction of residual nitrite and adjustment of the pH to neutrality. This system was useful for the study of ureas, which are stable in acid but not in neutral media. The range of responses covered more than two orders of magnitude. Most amino acids and primary amines also gave positive results, but could be assessed only after analysing the kinetics of the competing reactions and choosing appropriate reaction times. In a third system, Salmonella typhimurium strain TA1OO replaced NBP. Representatives of the class of amino acids, ureas, the primary amine tryptamine, and aniline became higbly mutagenic upon nitrosation. Methylguanidine was only weakly mutagenic under the present assay conditions. The results indicate that further studies with unstable nitrosation products of dietary components are required to understand more thoroughly the role of endogenous nitrosation in gastric cancer. KW - Medizin Y1 - 1987 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-86194 ER - TY - CHAP A1 - Shephard, S. E. A1 - Schlatter, C. A1 - Lutz, Werner K. T1 - Model risk analysis of nitrosatable compounds in the diet as precursors of potential endogenous carcinogens N2 - The potential health risk posed by the endogenous formation of N-nitroso compounds (NOC) from nitrosation of dietary ureas, guanidines, amides, amino acids and amanes (primary, secondary and aromatic) was estimated according to the model: Risk = ( daily intake of precursor] X (gastric concentration of nitrite ]n X [nitrosatability rate constant] X [cilrcinogenicity of derivative]. The daily intakes ofthese compound classes span five orders ofmagnitude (100 g/day amides, top; 1-10 mg/day secondary amines, ureas, bottom); the nitrosation rate constants span seven orders of magnitude (aryl amines, ureas, top; amides, secondary amines, bottom); and the carcinogenicity estimates span a 10 000-fold range from 'very strong' to 'virtually noncarcinogenic'. The resulting risk estimates likewise span an enormous range (nine orders of magnitude ): dietary ureas and aromatic amines combined with high nitrite concentration could pose as great a risk as the intake of preformed N-nitrosodimethylamine in the diet. In contrast, the risk posed by the in-vivo nitrosation of primary and secondary amines is probably negligible. The risk contributed by amides (including protein), guanidines and primary amino acids is intermediate between these two extremes. KW - Risikoanalyse KW - Carcinogen KW - Ernährung Y1 - 1987 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-86188 ER - TY - CHAP A1 - Klotz, Karl-Norbert A1 - Keil, Roger A1 - Zimmer, Franz-Josef A1 - Schwabe, Ulrich T1 - Modulation of (§H) DPCPX binding to membrane-bound ans solubilized A1 adenosine receptors by guanine nucleotides N2 - No abstract available KW - Adenosinrezeptor Y1 - 1989 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-86153 ER - TY - CHAP A1 - Spielmann, W. S. A1 - Arend, L. J. A1 - Klotz, Karl-Norbert A1 - Schwabe, U. T1 - Adenosine control of the renal Collecting tubule: receptors and signaling N2 - No abstract available. KW - Adenosin Y1 - 1991 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-86129 ER - TY - CHAP A1 - Spielmann, W.-S. A1 - Arend, L. J. A1 - Klotz, Karl-Norbert A1 - Schwabe, U. T1 - Adenosine receptors and singnaling in the kidney N2 - No abstract available. KW - Adenosinrezeptor KW - Niere Y1 - 1990 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-86114 ER - TY - CHAP A1 - Lohse, Martin J. A1 - Klotz, Karl-Norbert A1 - Maurer, K. A1 - Ott, I. A1 - Schwabe, Ulrich T1 - Effects of adenosine on mast cells N2 - No abstract available KW - Adenosin KW - Mastzelle Y1 - 1990 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-86101 ER - TY - CHAP A1 - Weinert, Franz E. A1 - Helmke, Andreas A1 - Schneider, Wolfgang T1 - Individual differences in learning Performance and in school achievement: Plausible parallels and some unexplained discrepancies N2 - No abstract available. KW - Lernerfolg KW - Schulleistung Y1 - 1990 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-71210 ER - TY - CHAP A1 - Weinert, Franz E. A1 - Schneider, Wolfgang A1 - Knopf, Monika T1 - Individual differences in memory development across the life-span N2 - Experimental research on memory development has typically focused on the description of universal development trends across the life span and the identification of major sources of development within this domain. However, there is a lack of studies investigating the preconditions and effects of interindividual variability within age groups across different memory tasks. Similarly, our knowledge about the stability of interindividual differences across the life span as well as the sources and the amount of intraindividual variability across memory tasks is scarce. In the present chapter, we concentrate on these neglected issues. First, theoretical assumptions concerning the interindividual and intraindividual variability of memory development are discussed. Next, empirical evidence is presented that seems suited to document the importance of these neglected issues. While we try to give a representative account of the literature, the emphasis is on more recent studies of memory development in children and elderly adults conducted in our laboratory. The results demonstrate that age-related changes and individual differences in the knowledge base are particularly important for describing and explaining individual differences in memory develoment. In comparison, the rote of stable individual differences in basic memory capacities in explaining variations in memory development is less clear given tbe conflicting empirical evidence. In the final section of the chapter consequences for future research are discussed. KW - Gedächtnisbildung KW - Lebensalter Y1 - 1988 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-70666 ER - TY - CHAP A1 - Zimmermann, U. A1 - Stopper, Helga T1 - Electrofusion and electropermeabilization of cells N2 - No abstract available. KW - Elektrofusion KW - Elektroporation KW - Zelle Y1 - 1987 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-73065 ER -