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2001 (1)
1998 (2)
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    Stylianos Tsakiris3, Panagiota Kouniniotou-Krontiri3, KleopatraH. Schulpisb, JohnC. Stavridis3Requires cookie*
 Title    L-Phenylalanine Effect on Rat Brain Acetylcholinesterase and Na+,K+-ATPase  
 Abstract    The effect of different L-phenylalanine (Phe) concentrations (0 .1 -1 2 .1 m M) , on acetylcho­ linesterase (A C h E) and N a+,K +-ATPase activities of brain homogenate and pure enzymes, was investigated at 37 °C. A C h E and Na+,K +-ATPase activities were determined according to Ellman G. -6 1 3) respectively, after preincubation with Phe. A C h E activity in brain homogenate or in pure eel E.electricus enzyme showed a decrease, which reached up to 18% with concentrations of 0 .9 -1 2 .1 m M . Brain homogenate N a+,K +-A TPase activity showed an increase 1 6 -6 5 % with 0 .2 4 -0 .9 mM of Phe, while an activity increase of 6 0 -6 5 % appeared with 0 .9 -1 2 .1 mM of Phe. Pure en­ zyme activity (from porcine cerebral cortex) was not affected by high Phe concentrations, while it was increased by low concentrations. The above results suggest: a) A direct effect of Phe on A C h E , b) A direct effect of low Phe concentrations and an indirect effect of high ones on Na+,K +-ATPase. 
  Reference    Z. Naturforsch. 53c, 163 (1998); received September 22/D ecem ber 15 1997 
  Published    1998 
  Keywords    L-Phenylalanine, R at Brain, Acetylcholinesterase, N a+, K +-ATPase, Mg2+-ATPase 
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 TEI-XML for    default:Reihe_C/53/ZNC-1998-53c-0163.pdf 
 Identifier    ZNC-1998-53c-0163 
 Volume    53 
3Author    Stylianos Tsakiris, Panagoula Angelogianni, JohnC. StavridisRequires cookie*
 Title    Effect of Aging on the Activities of Acetylcholinesterase, Na+, K+-ATPase and Mg2+-ATPase in Rat Pituitary and Hypothalamus  
 Abstract    Acetylcholinesterase (A C h E), N a+, K +-ATPase and Mg2+-A TPase activities were esti­ mated in homogenised rat pituitary and hypothalamus of 4-and 22-month-old rats. A C hE activity was not altered in the pituitary of aged com pared to adult rats, while it was found decreased by about 40% in the hypothalamus. N a+,K +-A TPase activity remained stable in the hypothalamus, while it was decreased by about 38% in the pituitary. Mg2+-A TPase activ­ ity remained unchanged in the hypothalamus, but was increased by about 83% in the pitu­ itary. This pituitary N a+, K +-ATPase inactivation may result in pathological mood and de­ creased neural excitability and metabolic energy production in aged animals.The age-related alterations of A C h E , Na+, K +-ATPase and Mg2+-A TPase activities may reflect changes in secretion and responses of some hormones of pituitary and hypothalamus. 
  Reference    Z. Naturforsch. 53c, 168 (1998); received O ctober 13/O ctober 31 1997 
  Published    1998 
  Keywords    Aging, R at Pituitary, Rat Hypothalamus, Acetylcholinesterase, N a+, K +-ATPase, Mg2+-ATPase 
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 TEI-XML for    default:Reihe_C/53/ZNC-1998-53c-0168.pdf 
 Identifier    ZNC-1998-53c-0168 
 Volume    53