A NEW FORM OF OVINE G(M1)-GANGLIOSIDOSIS

Neurological signs were observed in 3 lambs at approximately 1 month o f age, in a flock of 1 ram and 29 ewes with 43 lambs. Deterioration oc curred such that the lambs had either died or been killed by 4 months of age. Necropsies of two of these lambs revealed a diffuse encephalop athy in which the most prominent feature was ballooned neurons. Sectio ns of frozen brain showed PAS-positive, oil red O-negative, and weak S udan Black-positive material in the swollen neuronal cytoplasm. The ul trastructure of the neuronal inclusions showed characteristic whorled membranes, suggesting diagnosis of a gangliosidosis. The underlying en zymic defect was investigated by assaying 11 lysosomal enzymes in extr acts of kidney from an affected lamb and from normal lambs. A deficien cy (90%) of acidic beta-D-galactosidase was found in the affected lamb . All other activities, including N-acetylneuraminidase, were normal. A specific deficiency of lysosomal beta-D-galactosidase was demonstrat ed by separating the lysosomal and cytosolic beta-D-galactosidase by c hromatography on concanavalin A-Sepharose. Diagnosis of G(M1)-ganglios idosis, analogous to the severe infantile form of the human disease, w as made on the basis of the pathology and enzymology. The beta-D-galac tosidase activity in the white blood cells of the ram and several of t he ewes was consistent with their being heterozygotes. This disorder i s different from a previously described lipidosis in sheep, in which t here was a combined deficiency of beta-D-galactosidase and alpha-neura minidase.