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Sökning: WFRF:(Zhang P) > (1990-1994)

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1.
  • Lundgren, Johan, et al. (författare)
  • Acidosis-induced ischemic brain damage: are free radicals involved?
  • 1991
  • Ingår i: Journal of Cerebral Blood Flow and Metabolism. - 1559-7016. ; 11:4, s. 587-596
  • Tidskriftsartikel (refereegranskat)abstract
    • Substantial evidence exists that reactive oxygen species participate in the pathogenesis of brain damage following both sustained and transient cerebral ischemia, adversely affecting the vascular endothelium and contributing to the formation of edema. One likely triggering event for free radical damage is delocalization of protein-bound iron. The binding capacity for some iron-binding proteins is highly pH sensitive and, consequently, the release of iron is enhanced by acidosis. In this study, we explored whether enhanced acidosis during ischemia triggers the production of reactive oxygen species. To that end, enhanced acidosis was produced by inducing ischemia in hyperglycemic rats, with normoglycemic ones serving as controls. Production of H2O2, estimated from the decrease in catalase activity after 3-amino-1,2,4-triazole (AT) administration, was measured in the cerebral cortex, caudoputamen, hippocampus, and substantia nigra (SN) after 15 min of ischemia followed by 5, 15, and 45 min of recovery, respectively (in substantia nigra after 45 min of recovery only). Free iron in cerebrospinal fluid (CSF) was measured after ischemia and 45 min of recovery. Levels of total glutathione (GSH + GSSH) in cortex and hippocampus, and levels of alpha-tocopherol in cortex, were also measured after 15 min of ischemia followed by 5, 15, and 45 min of recovery. The results confirm previous findings that brief ischemia in normoglycemic animals does not measurably increase H2O2 production in AT-injected animals. Ischemia under hyperglycemic conditions likewise failed to induce increased H2O2 production. No difference in free iron in CSF was observed between animals subjected to ischemia under hyper- and normoglycemic conditions. The moderate decrease in total glutathione or alpha-tocopherol levels did not differ between normo- and hyperglycemic animals in any brain region or at any recovery time. Thus, the results failed to give positive evidence for free radical damage following brief periods of ischemia complicated by excessive acidosis. However, it is possible that free radical production is localized to a small subcellular compartment within the tissue, thereby escaping detection. Also, the results do not exclude the possibility that free radicals are pathogenetically important after ischemia of longer duration.
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3.
  • Szymanski, J. J., et al. (författare)
  • MEGA : A search for the decay mu –> e gamma
  • 1994
  • Ingår i: Intersections between particle and nuclear physics. Proceedings, 5th Conference, St. Petersburg, USA, May 31-June 6, 1994. ; , s. 789-792
  • Konferensbidrag (refereegranskat)
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4.
  • Yi, H R, et al. (författare)
  • Improved step edges on LaAlO3 substrates by using amorphous carbon etch masks
  • 1994
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 65, s. 1177-1179
  • Tidskriftsartikel (refereegranskat)abstract
    • We report a technique for the fabrication of sharp and straight step edges on LaAlO3 (LAO) substrates by ion milling. An electron beam lithography defined amorphous carbon film was used as an etch mask. It had very low ion milling rate and was easily prepared and removed. Atomic force microscopy was used to determine the step profile. YBa2Cu3O7 step edge junctions fabricated at the LAO steps show promising results. An IcRn product of 1 mV was obtained at 30 K. A Fraunhofer-like magnetic field dependence of Ic was obtained up to ±2 0. One weak link or possibly identical weak links in series for these step edge junctions were observed from the current-voltage (I-V) curves as well as from the magnetic field dependence of the I-V curves. Applied Physics Letters is copyrighted by The American Institute of Physics.  
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