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DNA could readily associate with the aggregated forms of the beta-amyloid peptides beta(1-40) and beta(25-35), giving rise to a shift in the electrophoretic mobility of DNA. As a result, DNA was retained at the top of a 1% agarose gel. In contrast, the electrophoretic mobility of DNA was little influenced by the monomeric forms of beta(1-40) and beta(25-30). DNA from different sources such as lambda phage, Escherichia coli plasmid, and human gene showed similar results. However, the electrophoretic mobility of RNA was shifted by the monomeric beta(1-40) and beta(25-35) as well as by the aggregated beta(1-40) and beta(25-35). The association of DNA with the aggregated beta-amyloid peptides could occur at pH 4-9. The inhibitory action of hemin on beta-amyloid aggregation could be confirmed using the DNA mobility shift assay. These results indicate that the DNA mobility shift assay is useful for kinetic study of beta-amyloid aggregation as well as for testing of agents that might modulate beta-amyloid aggregation., (Copyright 2000 Academic Press.)

The level of nitrite accumulation in the culture media of astrocytes activated with lipopolysaccharide (LPS) and interferon-gamma (IFN) was decreased by pretreatment of cells with LY294002, a quercetin derivative developed for phosphatidylinositol-3-kinase (PI3K) inhibitor, in a dose-dependent manner. The expression of iNOS mRNA in the astrocytes was inhibited by LY294002, as revealed by reverse transcriptional polymerase chain reaction and agarose gel electrophoresis. The catalytic activity of astrocytic iNOS was also inhibited by LY294002. On the other hand, wortmannin which was known to enhance endotoxin-induced NO production in macrophages by inhibiting PI3K did not cause any significant change in the NO production and iNOS mRNA expression of the astrocytes. These results suggest that LY294002 suppresses NO production in the astrocytes through not only the inhibition of iNOS mRNA expression but also the inhibition of the iNOS activity and that PI3K is not involved in the inhibitory actions of LY294002.pc 1999 Academic Press@p$hr, (Copyright 1999 Academic Press.)