Rats were subjected to cardiac arrest and resuscitation, 90 min of reperfusion, and in situ perfusion fixation. Thiobarbituric acid (TBA) was included in the aldehyde-free perfusion fixative, the TBA reaction was driven in situ by heating, and fluorescence microscopy was utilized to characterize the location of products of the TBA reaction. Absorbance-difference spectra were performed on butanol-extracted brain homogenates to confirm in situ formation of TBA adducts with aldehydic products of lipid peroxidation. Nissl-stained sections revealed good cellular fixation without shrinkage artifacts. Fluorescence was not seen microscopically when TBA was omitted from the perfusion fixative, and little fluorescence was present in normal brains or brains after ischemia only. However, after 90-min reperfusion, intense granular fluorescence was seen in the neuronal perikarya (especially at the base of the apical dendrite) of numerous pyramidal neurons in cortical layers 5 and 6 and in the pyramidal layer of Ammon's horn in the hippocampus. The nuclei of these cells exhibited no fluorescence. Fluorescence was also present in some striatal neurons, but was absent in the adjacent radial bundles. Neither glia nor white matter exhibited similar fluorescence. These observations indicate that neurons in the selectively vulnerable zones of the cortex and hippocampus are early and specific targets of lipid peroxidation during post-ischemic reperfusion.
The neocortex and the hippocampus were examined for lipid peroxidation products and ultrastructural alterations by fluorescence and electron microscopy, respectively, in rats subjected to 10 min of cardiac arrest or 10 min cardiac arrest and either 90 or 360 min reperfusion. Lipid peroxidation products were observed after 90 min reperfusion in the perikarya and proximal dendrites of neocortical pyramidal neurons and in the hippocampal hilar cells and CA1, region; the fluorescence was most intense at the base of the apical dendrite, the region of the Golgi apparatus. After 90 min of reperfusion, the CA1, showed considerable stretches of rough endoplasmic reticulum devoid of ribosomes and the Golgi cisternae were shorter and widely dilated. The neocortex showed similar endoplasmic reticulum changes, but no significant alterations to the Golgi were noted. In addition there were areas where strings of ribosomes appear to be detaching from the endoplasmic reticulum. After 360 min reperfusion in both the neocortex and the hippocampus, the damage appeared more severe. The Golgi was fragmented into vacuoles, membranous whorls had appeared, and dense aggregates of smooth vesicles were seen coalescing with each other and the vacuoles. These observations suggest that early Golgi involvement is a more important marker of lethal injury than ribosome release from the endoplasmic reticulum. The areas of disturbed Golgi ultrastructure correspond to those areas that show evidence of lipid peroxidation and imply that lipid peroxidation may be causally related to the disturbance in Golgi ultrastructure.
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