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  • 1990-1994  (2)
  • Aging  (1)
  • Illuminationeffect  (1)
  • Platelet-activating factor  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Density-associated changes in platelet-activating factor acetylhydrolase activity and membrane fluidity of human erythrocytes (1994)
    Springer
    Annals of hematology 69 (1994), S. 139-145 
    Details
    ISSN: 1432-0584
    Keywords: Aging ; Erythrocytes ; Platelet-activating factor ; Acyltransferases ; Membrane fluidity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Platelet-activating factor acetylhydrolase is known to degrade oxidatively fragmented phospholipids which are similar in structure to platelet-activating factor. We examined changes of acetylhydrolase activity during in vivo aging of human erythrocytes and tried to assess its role in maintaining the membrane properties of erythrocytes. Higher-density erythrocytes are enriched with older cells. Erythrocytes obtained from seven healthy colleagues were separated into four density fractions by centrifugation in discontinuous Percoll density gradients. Both membrane and cytosolic acetylhydrolase decreased with increasing erythrocyte density. Membrane and cytosolic acetylhydrolase activities in the lightest fraction were 2.0±1.0 (SD) nkat/g protein and 362±58 pkat/g protein, respectivley, and these values were significantly higher than those in the densest fraction: 1.3±0.7 nkat/g protein and 286±70 pkat/g protein, respectively. Membrane acyltransferase activity also decreased with red cell density and the average values in the lightest and densest fractions were 51.2±23.6 and 27.0±20.2 μkat/g protein, respectively. Generation of thiobarbituric acid-reactive substances induced byt-butyl hydroperoxide treatment decreased with increasing cell density, and the inhibition of acetylhydrolase with diisopropylfluorophosphate resulted in enhanced peroxide-induced lipid oxidation, particularly in lower-density fractions. There was no significant change in basal levels of thiobarbituric acid-reactive substances in red cell membrane. Membrane fluidity was evaluated by fluorescence recovery after photobleaching and it decreased as erythrocyte density increased. We conclude that the activity of the deacylation/reacylation cycle maintained by acetylhydrolase and acyltransferase is gradually reduced during in vivo aging of erythrocytes. This may be connected with decreases of polyunsaturated fatty acids and membrane fluidity in old eryhtrocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01695695
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    CPS GL 799 (1991)
    Springer
    Colloid & polymer science 269 (1991), S. 70-76 
    Details
    ISSN: 1435-1536
    Keywords: Illuminationeffect ; adsorption ; diffusion ; cellulosemembrane ; directdye
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The effect of illumination on transport of sulfonated bisazo direct dyes, CI Direct Yellow 12, and CI Direct Yellow 4, into a cellulose membrane has been studied at various temperatures. Transport of CI Direct Yellow 12, which exhibits photoinduced reversible trans-cis isomerism in aqueous solution into a cellulose membrane, was influenced by illumination. It is likely that the transport was influenced by transisomerization of the photoisomeric dye and the diffusivity was controlled by surface diffusion rather than by pore diffusion under both light and dark conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00654661
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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