Tay-Sachs disease: generalized absence of a beta-D-N-acetylhexosaminidase component

Two hexosaminidase components, separable by starch-gel electrophoresis and possessing both beta-D-N-acetylglucosaminidase and beta-D-N-acetylgalactosaminidase activity, are present in human tissues. One of these, hexosaminidase component A, is absent in brain, liver, kidney, skin, cultured skin fibroblasts, blood plasma, and leukocytes from nine patients with Tay-Sachs disease. Hexosaminidase assay may facilitate the early diagnosis of individuals homozygous for Tay-Sachs disease.

Radiation-induced breaks of DNA in cultured mammalian cells

Mouse leukemic cells (L5178Y) in suspension culture were irradiated and the extent of single-strand breaks and double-strand cuts of DNA was estimated by sucrose gradient centrifugation. The radiation produced 3.0 single-strand breaks per cell (G(1) stage) per rad and approximately 0.3 double-strand breaks per cell (G(1) stage) per rad.

Generalized gangliosidosis: impaired cleavage of galactose from a mucopolysaccharide and a glycoprotien

We have demonstrated a tenfold (or greater) reduction of the cleavage of galactose from a mucopolysaccharide and a glycoprotein in generalized gangliosidosis, a lysosomal beta-galactosidase deficiency disease. The bony abnormalities in this disease may be due to defective catabolism of mucopolysaccharides in connective tissue.

Effective specific activity dilution in labeled DNA of cultured mammalian cells (L5178Y)

Upon labeling the DNA of cultured mammalian cells with radio-active thymidine it was found that there was a large reduction in the specific activity of radioactive thymidine in DNA when this specific activity was compared to the specific activity of the exogenous supply. This reduction in specific activity may be determined once the effective dilution factor for thymidine in mammalian cells is known. The average effective dilution factor was found to be 2 x 10(-4) M for L5178Y cells in log growth.

Growing points of DNA in cultured mammalian cells

A fraction of DNA, known to be replicating, was examined in the electron microscope. Characteristic branch points were identified as sites at which replication had been taking place. No localized strand separations, nor other structural alterations were discernible at these points.