Neuropathological lesions in experimental lead toxicosis of dogs.

Light microscopical examinations were carried out on the central and peripheral nervous systems of 9 dogs maintained on a high-fat-low-calcium diet and dosed orally with a mixture of lead chloride, lead bromide and lead sulphate. Microscopic lesions were present in 7 (78 per cent) of the lead-treated dogs. Cerebrocortical lesions comprising spongiosis, vascular hypertrophy and gliosis predominated. These lesions were bilateral, had a predilection for gyri and were located mainly in the parietal and frontal cortex. There were bilaterally symmetrical spongiform changes in the brain stem. The cerebellum had spongiform changes in the roof nuclei and in the lingula there was spongiosis of the Purkinje cell layer and vacuolation of Purkinje cells. Axonal degeneration was evident in a sciatic nerve of one dog. In a second experiment, designed to study the early ultrastructural changes in the brains of dogs with lead intoxication, 2 groups of dogs, one on a commercial balanced diet and the other fed a high-fat-low-calcium diet, were given similar amounts of lead. Cytoplasmic accumulation of lipid was found in the cerebrovascular pericytes of all dogs treated with lead but vascular changes were otherwise not obvious. Quantitative evaluation of numbers of blood vessels by light microscopy revealed an apparent increase in all dogs receiving lead. This increase in vascularity was greatest in the dogs fed the high-fat-low-calcium diet.