Hydroxyl radicals generated either by redox cycling a toxin utilizing endogenous enzymes, or as a result of metabolism which has been activated by a toxin, may be involved in the pathogenesis of neurodegenerative disorders. Oxidative damage to neuronal DNA could result in impaired neuronal function if the damage remained unrepaired and accumulated. In order to measure DNA damage, either neuronal or mitochondrial, gas chromatographic-mass spectrometric methods are being improved for the detection of thymine glycol, one of the oxidation products of thymine. Radiolabelled thymine glycol and thymidine glycol have been prepared to permit quantitative determination of yield. A high sensitivity negative chemical ionization mass spectrometric assay of platelet activating factor is being used in conjunction with studies of quinolinate accumulation in cell and animal models of neuropathology accompanying inflammation. The gerbil cerebral ischemia model is being used for in vivo assessment; the chick ciliary ganglion is being explored as an in vitro model known to be quinolinate sensitive. Two collaborative studies on the identification of unknown biologically active materials are in progress - a pituitary derived cytotrophic factor, and a brain or plasma derived benzodiazepine ligand binding substance. In both studies, on-line chromatography and various mass spectrometric techniques are being used to identify materials from complex mixtures that have been extensively chromatographed, but still contain interfering substances.