Neuraminidase in mucolipidoses: normal activity in frozen autopsy tissues from three patients with I-cell disease and adult beta-galactosidase deficiency

Neuraminidase was assayed in the frozen autopsy tissues from three patients with I-cell disease and an adult patient with cherry-red spots, myoclonus, cerebellar ataxia and beta-galactosidase deficiency. Both diseases showed normal neuraminidase activity toward neuramine lactose and fetuin in cerebral gray matter, liver and kidney. These results suggest that the neuraminidase deficiency is limited only to some tissues and that this biochemical abnormality is not caused by a primary genetic mutation in these diseases.

Differential activities of glycolipid glycosyltransferases in Tay-Sachs disease: studies in cultured cells from cerebrum

Four different glycolipid:glycosyltransferase activities involved in the biosynthesis in vitro of gangliosides and blood group-related glycosphingolipids have been tested in a simian virus 40-transformed glial cell culture derived from the cerebrum of a fetus with Tay-Sachs disease (TSD). The TSD cultured brain cells contained little activity of either UDP-Gal:GM2(beta 1-3)galactosyltransferase (GalT-3; EC 2.4.1.62), which catalyzes the formation of GM1a from GM2 (tay-Sachs) ganglioside, or GDP-Fuc:nLcOse4Cer (alpha 1-2)fucosyltransferase (FucT-2; EC 2.4.1.89), which catalyzes the formation of H1 glycolipid from nLcOse4Cer. These cells contained a potent inhibitor of the second reaction (catalyzed by a Golgi-rich membrane fraction from bovine spleen), whereas no inhibition of the first reaction (catalyzed by a membrane fraction from 14-day-old embryonic chicken brain) was observed. The activity of UDP-Gal:LcOse3Cer(beta 1-4)galactosyltransferase (GalT-4; EC 2.4.1.86) was 30- to 80-fold higher than the activity of GalT-3. The presence of CMP-AcNeu:nLcOse4Cer sialyltransferase activity and the absence of either GalT-3 or FucT-2 suggested a probable pathway for the synthesis of sialylneolactotetraosylceramide [GM1b(GlcNAc)] in addition to a specific blockage of GM1a ganglioside synthesis from GM2 in these TSD transformed cells.

Human hexosaminidase isozymes. IV. Effects of oral contraceptive steroids on serum hexosaminidase activity

Data from a mass screening program for identification of persons who are heterozygous for Tay-Sachs disease have been analyzed for the effects of oral contraceptive steroids on the activity in serum of hexosaminidase (hex) and the various hex isozymes. Women using oral contraceptives show a significantly higher total serum hex activity, reflecting mainly an increase in the heat-stable hex isozyme (hex I), and a smaller increase in the heat-labile hex A than do women using no medications. The changes in women using oral contraceptives are qualitatively similar to those observed during pregnancy. The distribution of responses to oral contraceptives is unimodal, and some of the variations may be related to differences in amount of steroid ingested. In addition, underlying genetic variation may contribute to the observed differences in enzyme activities.

Demonstration of cross-reacting material in Tay-Sachs disease

Antibodies against placental hexosaminidase A and kidney alpha-subunits were raised in rabbits after cross-linking the antigens with glutaraldehyde. Anti-(alpha(n)-subunit) antiserum (anti-alpha(n)) precipitated hexosaminidase A but not hexosaminidase B, whereas anti-(hexosaminidase A) antiserum precipitated both hexosaminidases A and B. Specific anti-(hexosaminidase A) antiserum was prepared by absorbing antiserum with hexosaminidase B. Both anti-alpha(n) and anti-(hexosaminidase A) antisera precipitated the CR (cross-reacting) material from eight unrelated patients with Tay-Sachs disease. Immunotitration, immunoelectrophoresis, double-immunodiffusion and radial-immunodiffusion techniques were used to demonstrate the presence of CR material. The CR-material-antibody complex was enzymically inactive. Antiserum raised against kidney or placental hexosaminidase A, without cross-linking with glutaraldehyde, failed to precipitate the CR material, implying that treatment of the protein with glutaraldehyde exposes antigenic determinants that are hidden in the native protein. Since anti-(hexosaminidase B) antiserum did not precipitate the CR material during the immunoelectrophoresis of Tay-Sachs liver extracts, it is suggested that altered alpha-subunits do not combine with beta-subunits. By using immunotitration we have demonstrated the competition between the hexosaminidase B-free Tay-Sachs liver extract and hexosaminidase A for the common binding sites on monospecific anti-(cross-linked hexosaminidase A) antiserum. The amount of CR material in the liver samples from seven cases of Tay-Sachs desease was found to be in the same range as theoretically calculated alpha-subunits in normal liver samples. Similar results were obtained by the radial-immunodiffusion studies. The present studies therefore suggest that Tay-Sachs disease is caused by a structural-gene mutation.

Enzyme replacement in Tay-Sachs disease

Enzyme replacement therapy was attempted with two Tay-Sachs-diseased individuals--a 14-month-old child and a 7-week-old infant. Treatment consisted of repeated weekly intrathecal injections of pure hexosaminidase A. Injection of this enzyme resulted in almost complete disappearance of GM2 from the serum, but did not bring about dissolution of the GM2 membranous cytoplasmic bodies in the brain, as detected by electronmicroscopy. Both patients tolerated the treatment without apparent clinical complications, but no clear-cut improvement was noted as a result of prolonged injections of hexosaminidase A. Since this treatment was initiated in both an advanced stage and a very early stage of the disease, we conclude that enzyme replacement treatment by this route is not beneficial for patients with Tay-Sachs disease.

Serum beta-hexosaminidases in pregnancy

Serum contains several hexosaminidase forms. Two, HEX A and HEX B, migrate in both DEAE cellulose and isoelectric focussing systems like their tissue counterparts. A major group of serum hexosaminidases migrate in an intermediate position. These forms, collectively named HEX 1, increase during pregnancy and obscure carrier detection for Tay-Sachs and Sandhoff's disease. Using DEAE-cellulose chromatography, HEX A, I, and B, can be clearly separated. In normals, activity ratios of A/B are 4.03 +/- 1.33. During pregnancy the ratio falls slightly to 3.01 +/- 1.08. In Tay-Sachs heterozygotes the ratio is only 1.08 +/- 0.35 and falls during early pregnancy to 0.53 +/- 0.23. In Sandhoff heterozygotes the DEAE chromatograms appear normal with higher than normal A/B ratios but in sera, from both pregnant and nonpregnant carriers, the HEX B and HEX I forms are 50% heat labile. During pregnancy, serum can be used as a reliable source of HEX for heterozygote identification for both Sandhoff's and Tay-Sachs disease.

Use of microtechniques for the detection of lysosomal enzyme disorders: Tay-Sachs disease, Gm1-gangliosidosis and Fabry disease

A preliminary report on the use of microtechniques for the detection of three lysosomal storage diseases (Tay-Sachs, GM1-gangliosidosis and Fabry disease) is presented. This microassay method uses from 100 to 300 cultured amniotic fluid cells or skin fibroblasts. A comparison between values for total activity and heat inactivated forms of hexosaminidase (in Tay-Sachs disease) is presented. The feasibility of the use of this microtechnique in prenatal diagnosis is discussed.

Psychosocial aspects of a Tay-Sachs screening clinic

The authors administered questionnaires to participants in a Tay-Sachs screening clinic. They received 322 responses. Although the majority of the respondents expressed anxiety about the possibility that they might be carriers, most indicated that this anxiety brought them to the clinic. The authors conclude that a well-publicized and well-organized screening clinic can function successfully and deal with the issue of anticipated loss without producing mass fear. An important factor in their clinic was the fact that they were able to offer an alternative to a Tay-Sachs child through amniocentesis.

Sphingolipidoses

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