Spatial dispersion of stainable lipid in frozen sections of human aorta.

Frozen sections of human lateral thoracic aorta were stained for lipid with Oil red O. Intensity of staining was judged upon a scale of 0 to 5 brilliance units by matching to a scale of photographs. Microregions, defined by an eyepiece grid, were structured in layers of 100 microns thickness and 1000 microns along the aortic length. The intensity of staining, both total and extracellular, tended significantly to increase with age, intimal thickness and depth into the intima. Aortas having at least one instance of atheronecrosis tended to show generally greater staining intensities than aortas without necrosis, and the tendency was more conspicuous with total than with extracellular staining, implying a greater degree of intracellular staining in the specimens with atheronecrosis. The evidence seems to suggest that the emergence of a necrotic core happens, at least in part, because the affected site has collected an excess of lipid. The evidence further suggests that lipid deposits become excessive with increasing frequency after age 35 years, and that this is associated with intimal thickenings coming to exceed 300 microns. The causes that propel the intimal thickenings remain wholly unknown - those causes seem to have little if anything to do with excess of lipids. Some as yet undetermined qualitative characteristic of the lipids might be of importance in this regard.