GM1 gangliosidosis type 2 in two siblings.

A sister and brother, now aged 7 and 9 years, presented with developmental arrest, gait disturbance, dementia, and a progressive myoclonic epilepsy syndrome with hyperacusis in the second year of life. Then, spastic quadriparesis led to a decerebrate state. In the absence of macular or retinal degeneration, organomegaly, and somatic-facial features suggesting mucopolysaccharidosis, the presence of hyperacusis together with sea-blue histiocytes in bone marrow biopsies and deficient beta-galactosidase activity but normal glucosidase, hexosaminidase, and neuraminidase activity on lysosomal enzyme assays constitutes the clinical-pathologic-biochemical profile of GM1 gangliosidosis type 2. This is a rare, late infantile onset, progressive gray-matter disease in which beta-galactosidase deficiency is largely localized to the brain, though it can be demonstrated in leukocytes and cultured skin fibroblasts. It must be distinguished from the Jansky-Bielschowsky presentation of neuronal ceroid lipofuscinosis, mitochondrial encephalopathy, lactic acidosis, strokelike episodes (MELAS) and myoclonic epilepsy with ragged-red fibers (MERRF) syndromes, atypical presentations of GM2 gangliosidoses (Tay-Sachs and Sandhoff's diseases), primary sialidosis (neuraminidase deficiency), galactosialidosis, and Alpers' disease.

Incorporation of exogenous ganglioside GM1 into neuroblastoma membranes: inhibition by calcium ion and dependence upon membrane protein.

Since exogenous gangliosides are known to promote neuritogenesis, the incorporation of exogenous GM1 into neuroblastoma membranes was examined. Neuro-2A cells, synchronized in the G1/G0 phase, were suspended in HEPES buffered saline containing 10(-4) M [3H]GM1, and membrane incorporation was measured as radioactivity remaining with the cell pellet following incubation with serum-containing medium and trypsin. Calcium ion (0.01 to 10 mM) reduced incorporation of exogenous GM1, due to its interaction with GM1 micelles in solution. When cells were treated with proteases prior to incubation with GM1, the inhibitory effect of Ca2+ was lost and total incorporation into membranes was lowered by approximately one order of magnitude. Pretreatment of cells with 0.05% trypsin resulted in an inhibition of GM1 incorporation within 5 minutes. When trypsinized cells were resuspended in complete growth medium, the cells recovered the ability to incorporate GM1 with time, and this paralleled labeling of cellular protein with [3H]leucine. The role of membrane protein in the incorporation of exogenous GM1 could not be explained by the lytic release of cytosolic transfer proteins nor the artifactual coating of the cell surface by serum proteins. These results suggest that the incorporation of exogenous gangliosides into cellular membrane lipid bilayers cannot be fully explained by considerations of lipophilicity alone, and leads us to propose that initial recognition by membrane protein(s) is necessary.

Glycosphingolipid biosynthesis during myogenesis of rat L6 cells in vitro.

Glycosphingolipid biosynthesis was examined using [3H]-galactose as a precursor as rat L6 myoblasts fused to form multinucleated myotubes. Incorporation of label into neutral glycolipids decreased steadily as the population of myotubes increased, so that final biosynthesis was one-half that observed with myoblasts (p less than 0.02). Conversely, ganglioside biosynthesis doubled during myoblast confluency (p less than 0.02) and then decreased as myotubes formed. Qualitatively, L6 cells synthesized large amounts of ganglioside GM3 during all myogenic phases. The major neutral glycosphingolipid products were lactosylceramide and paragloboside (nLcOse4Cer). Few changes in TLC autoradiographic patterns were noted during differentiation, with the exception of a slight decrease in ganglioside GM1. The results indicate that the biosynthesis of glycosphingolipids is tightly regulated during myogenesis in vitro and suggest a role for membrane gangliosides in muscle cell differentiation.

Lipid content of swine influenza and other vaccines.

An analysis of the lipids in swine influenza vaccines was performed, comparing six different lots of swine influenza, other influenza and noninfluenza vaccines. Cholesterol content and phospholipid content varied greatly, but there were no major differences between the types of vaccines. Appreciable amounts of phosphatidylethanolamine were found in only one swine influenza vaccine. The major phospholipids of influenza vaccines were phosphatidylcholine, sphingomyelin and phosphatidic acid. A detectable amount of phosphatidylserine was not found in any swine influenza vaccine, but was present in two of three nonswine influenza vaccines. Only two of six swine influenza vaccines showed trace amounts (less than 0.5 microgram/ml) of ganglioside (GM3). However, larger quantities of galactocerebroside were found (2.24-6.43 micrograms/ml) in all influenza vaccines examined, including swine influenza vaccines.

Phospholipid biosynthesis during normal and dystrophic avian muscle cell differentiation in culture.

The biosynthesis of phospholipids during differentiation of normal and dystrophic muscle cells was studied using [32Pi] added to primary culture media. Labeled phosphatides were separated by two-dimensional thin-layer chromatography, exposing the plates to HCl vapors between solvents to cleave the alk-1-enyl bonds. Phosphatidylethanolamine labeling did not vary during myotube formation. Although lower labeling of phosphatidylcholine was observed in dystrophic myoblasts at the single cell stage, no differences were observed between normal and dystrophic cultures after cell contact and myotube formation. A sharp decrease in phosphoinositide content was observed as myoblasts first achieved cell contact and continued to decline slowly as myotubes developed. During myogenesis, phosphatidylcholine content gradually increased, from 18.4% of the total labeled phospholipid in dividing myoblasts to 48.6% of the labeled phospholipids in fully differentiated myotubes.

Influence of mastitis on properties of milk. XI. Fat globule membrane.

The effect of mastitis on the milk fat globule membrane of milk samples from individual quarters was investigated. Wisconsin Mastitis Test positive (greater than 20mm) milk contained approximately 10% less milk fat globule membrane material than negative (smaller than 10mm) milk. The lipid portion of the milk fat globule membrane preparation from positive milk contained smaller amounts of phospholipids and larger amounts of cholesterol. Milk fat globule membrane preparations from positive milk had higher aldolase activity and lower xanthine oxidase activity. Dissociated membrane protein prepared from positive milk was resolved into five components by polyacrylamide gel electrophoresis while the membrane protein prepared from negative milk was resolved into three components.