Hepatic beta galactosidase and feline GMI gangliosidosis.

This paper describes the clinical, morphological and biochemical features of three cats with a progressive neurological disorder. Clinical features were ataxia and progressive tremor. The morphological characteristics were those of lysosomal storage disease affecting neurones of the central nervous system and autonomic ganglia; membranous cytoplasmic bodies were demonstrated by electron microscopy in cerebral neurones. Chemical analysis of brain from two of the cats revealed an increased content of total gangliosides, sialic acid and a specific increase in GMI ganglioside. Enzyme analysis of homogenates of leucocytes, spleen and brain showed less than 5% or normal 4-methylumbelliferyl-beta galactosidase (4MU-beta gal) activity. In liver, activity was markedly reduced at pH values below 4.2, but there was considerable activity above this value. The properties of 4MU-beta gal in normal and diseased feline livers were investigated. Sephadex gel filtration of diseased liver homogenates showed an absence of two thermolabile "acid' components, and reduced activity of a third thermostable "neutral' component. The biochemical abnormalities found in the diseased cats are similar to those found in human juvenile GMI gangliosidosis (type 2).