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2001 (1)
1985 (1)
1Author    Stylianos TsakirisRequires cookie*
 Title    Effects of L-Phenylalanine on Acetylcholinesterase, (Na+,K+)-ATPase and Mg2+-ATPase Activities in Adult Rat Whole Brain and Frontal Cortex  
 Abstract    The effect of different L-phenylalanine (Phe) concentrations (0.12-12.1 m M) on acetylcho­ linesterase (AChE), (Na+,K+)-ATPase and Mg2+-ATPase activities was investigated in ho-mogenates of adult rat whole brain and frontal cortex at 37 °C. AChE, (Na+,K+)-ATPase and Mg2+-ATPase activities were determined after preincubation with Phe. AChE activity in both tissues showed a decrease up to 18% (p<0.01) with Phe. Whole brain Na+,K+-ATPase was stimulated by 30-35% (p<0.01) with high Phe concentrations, while frontal cortex Na+,K+-ATPase was stimulated by 50-55% (pcO.OOl). Mg2+-ATPase activity was increased only in frontal cortex with high Phe concentrations. It is suggested that: a) The inhibitory effect of Phe on brain AChE is not influenced by developmental factors, while the stimulation of Phe on brain Na+,K+-ATPase is indeed affected; b) The stimulatory effect of Phe on rat whole brain Na+,K+-ATPase is decreased with age; c) Na+,K+-ATPase is selectively more stimulated by high Phe concentrations in frontal cortex than in whole brain homogenate; d) High (toxic) Phe concentrations can affect Mg2+-ATPase activity in frontal cortex, but not in whole brain, thus modulating the amount of intracellular Mg2+. 
  Reference    Z. Naturforsch. 56c, 132—137 (2001); received September 4/October 4 2000 
  Published    2001 
  Keywords    Acetylcholinesterase, (Na+, K+)-, Mg2 +-ATPase, L-Phenylalanine 
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 TEI-XML for    default:Reihe_C/56/ZNC-2001-56c-0132.pdf 
 Identifier    ZNC-2001-56c-0132 
 Volume    56 
2Author    M. Artin Bohl, Z. En, O. SimonRequires cookie*
 Title    MTD Approach to Quantitative Structure-Activity Relationships for Cardiotonic Steroids  
 Abstract    A minimal topological difference (MTD) approach is made to describe quantitative structure-activity relationships (OSAR) for the N a+, K+-ATPase inhibitory activity of cardiotonic steroids. The calculations take into account 20 derivatives of digitoxigenin, digoxigenin, and gitoxigenin with small substituents at different sites of the steroid backbone. A multiple correlation coeffi­ cient of r = 0.916 is obtained using the MTD and an indicator variable for the presence of a 15 ß substituent. The corresponding receptor map reveals receptor wall vertices in the C l l , C12, C15, and C22 regions. Both 3ß and 16ß substituents are found to contain receptor cavity vertices. The MTD results are discussed with respect to lactone-ring conformational investigations presented and they are compared with findings of previous structure-activity studies. 
  Reference    Z. Naturforsch. 40c, 858—862 (1985); received August 27 1985 
  Published    1985 
  Keywords    Receptor Site Mapping, MTD Method, Conformational Analysis, Cardiotonic Steroids, Na+, K -ATPase Inhibition 
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 TEI-XML for    default:Reihe_C/40/ZNC-1985-40c-0858.pdf 
 Identifier    ZNC-1985-40c-0858 
 Volume    40