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The oxidation of low-density lipoprotein (LDL) is implicated in atherosclerosis. Lipids and oxidized lipids were analysed by gas chromatography and gas chromatography-mass spectrometry in human LDL incubated with mouse peritoneal macrophages (MPM) or copper (II) sulphate in Ham's F-10 medium or medium alone (control). MPM-modification and copper-catalysed oxidation of LDL resulted in the formation of oxysterols, mainly cholest-5-en-3 beta,7 beta-diol (7 beta-OH-CHOL); 7%-19% of the initial cholesterol was converted to 7 beta-OH-CHOL in 24 h. 7 beta-OH-CHOL levels in control LDL were very low. The increase in 7 beta-OH-CHOL in MPM and copper-oxidized LDL was accompanied by decreases in linoleate and arachidonate and increases in the electrophoretic mobility and degradation of LDL protein by 'target' macrophages. The concerted occurrence of these processes and their similarity in both MPM-modification and copper-catalysed oxidation of LDL were suggested by the highly significant cross-correlations. The fall in polyunsaturated fatty acid (PUFA) was accompanied by a directly proportional increase in electrophoretic mobility of the LDL. Production of 7 beta-OH-CHOL and protein degradation by macrophages showed modest elevations during the initial steep fall in PUFA, and showed their greatest increases as the levels of PUFA slowly approached zero. The levels of 7 beta-OH-CHOL and the degradation of LDL by macrophages were directly proportional. The degradation of LDL by macrophages increased rapidly as the electrophoretic mobility of LDL was slowly approaching its maximum level.

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Production of [M+H]+ Ions Under Electron Ionisation Conditions bySelf-Induced Chemical Ionisation.During the operation of the SERC mass spectrometry service it was noticed that a very small number of compounds (approximately 10 out of 1400 examined), when introduced via a heated probe system under electron ionisation conditions, gave spectra in which the molecular ion was absent, but in its place a protonated molecular ion was present in excess of 10% of the base peak.

Meta-Topolin, a Highly Active Aromatic Cytokinin from Poplar Leaves ( Populus x canadensis Moench., cv. Robusta).-Title compound meta-topolin (I), a natural constituent of plant tissues together with its derivatives (II) and (III), is a new and highly active plant growth regulating substance.-(STRNAD, M.; HANUS, J.; VANEK, T.; KAMINEK, M.; BALLANTINE, J. A.; FUSSELL, B.; HANKE, D. E.; Phytochemistry 45