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During focal ischemia, neurons in a densely ischemic focus are usually doomed unless reperfusion is quickly instituted. In contrast, neurons in a less densely ischemic penumbral zone remain viable for at least 4-8 h and then die (Siesjo, 1992). Recent studies have provided evi dence that some neuronal subpopulations may die after permanent or transient cerebral ischemia via apoptosis or programmed cell death following the activation of an endogenous cell death program (Linnik et aI., 1993; Li et aI., 1995).The best characterized genetic system of programmed cell death (peD) is the worm Caenorhabditis elegans (c.

Background and Purpose: Increases in uric acid follow experimental stroke, which may be related to free radical formation by xanthine oxidase. The present study examined the time course of changes in xanthine and uric acid and their relationship to changes in the free radical scavengers glutathione, cysteine, and ascorbic acid.Methods: Focal ischemia was induced by occluding the middle cerebral artery, followed by transient occlusion of the common carotid arteries for 60 minutes. At varying time points, animals were sacrificed, and ischemic cortex was dissected. Neurochemical measurements were made by high-performance liquid chromatography with 16-sensor electrochemical detection.Results: Marked increases in uric acid were seen at all time points, with a maximal increase at 1 day and a persistent increase lasting up to 21 days. There were smaller reciprocal decreases in xanthine. Glutathione, cysteine, and ascorbic acid showed significant decreases, consistent with the generation of free radicals. Reductions in levels of cysteine and glutathione were significantly correlated with increases in uric acid levels.Conclusions: These findings confirm marked alterations in purine metabolism following focal ischemia and suggest that xanthine oxidase contributes to the generation of free radicals. (Stroke 1991;22:1548-1553)

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