PubMed Health⌕ Search

Biomedical subjects

R K Yu

Publications and source records attributed to R K Yu.

At least 253 records · Page 14Linked to original sources
PubMed1979

Isolation and characterization of two isomers of brain tetrasialogangliosides.

Two isomers of tetrasialogangliosides were isolated and purified to homogeneity from human, bovine, chicken, and cod fish brains by employing DEAE-Sephadex and Iatrobeads column chromatographies. The tetrasialogangliosides of human, bovine, and chicken brains appeared to be identical because they had identical mobilities on thin layer plates developed with six different solvent systems. The tetrasialoganglioside of cod fish brain moved slower on thin layer plates than the tetrasialoganglioside from the other species. The ganglioside preparations were subjected to mild acid hydrolysis, neuraminidase treatment, and periodate oxidation followed by borohydride reduction. The structures of the two isomers were differentiated from each other by controlled mild acid hydrolysis in both aqueous and organic solvents. The structure IV3(NeuAc)2,II3(NeuAc)2-GgOse4ceramide is assigned to the tetrasialoganglioside of human, bovine, and chicken brains; and the structure IV3NeuAc,II2(NeuAc)3-GgOse4ceramide is assigned to that of cod fish brain. The possible pathways for the synthesis of the two tetrasialogangliosides are discussed.

Animals↗
PubMed1979

Thyroid hormone influence on the susceptibility of mice to audiogenic seizures.

Serum thyroxine levels peak earlier and are significantly higher in audiogenic seizure-susceptible DBA/2J mice than in seizure-resistant C57BL/6J mice during early postnatal life. The seizure susceptibility of DBA/2J mice is suppressed by administration of an antithyroid drug or by radiothyroidectomy, while the seizure susceptibility of C57BL/6J mice is enhanced by treatment with excess thyroxine.

Acoustic Stimulation↗
PubMed1979

Genetic variability for regional brain gangliosides in five strains of young mice.

The quantitative and qualitative distributions of gangliosides were determined in the cerebrum, cerebellum, and brain stem of five inbred strains (C57BL/6J, DBA/2J, LG/J, C3H/HeJ, BALB/cJ) of mice at 21 days of age. Genetic differences were found among the strains for wet weight, absolute amount of gangliosides per region, and concentration of ganglioside (expressed on bolth a wet and a dry weight basis) in all three regions of the brain. The water content of the various brain regions showed the least amount of genetic variability. Coefficients of genetic determination were used to estimate the magnitude of genetic influence on these traits in each brain region. Significant differences were also found among the five strains for the distribution of certain gangliosides. The DBA strain, which is susceptible to audiogenic seizure at this age, had the highest level of the myelin-enriched ganglioside GM1 in all brain regions. Most of the genetic variation that influences the content and distribution of gangliosides among neurologically normal mice can be considered polygenic. Several possible sources of this genetic variation that may contribute to the differences observed among the strains are discussed.

Age Factors↗
PubMed1978

Assignment of the 13C nuclear magnetic resonance spectrum of aqueous ganglioside GM1 micelles.

This article describes the natural-abundance Fourier-transform carbon-13 nuclear magnetic resonance spectrum, at 67.88 MHz, of aqueous micelles of bovine brain ganglioside GM1 of purity greater than 99%. Assignments are given for every carbon nucleus in the molecule, on the basis of a comprehensive study of the relevant mono-, di-, tri-, and polysaccharides, including several containing sialic acid (5-acetamido-3, 5-dideoxy-D-glycero-D-galacto-nonulopyranosonic acid), and phospho-, sphingo-, and glycosphingolipids. These assignments represent an extension of the 13C nuclear magnetic resonance data from monosaccharides and lipids to complex oligosaccharides and glycolipids. They also form the basis for interpretation of spectral perturbations induced in GM1 by titration with paramagnetic europium(III). The single sialic acid in GM1 was found to be alpha-glycosidically linked in the oligosaccharide from considerations of its unique anomeric chemical shift. The sialic acid carboxyl and glyceryl side chain, along with additional ligands donated by the 2-acetamido-2-deoxy-beta-D-galactopyranoside and terminal beta-D-galactopyranoside residues in the oligosaccharide portion of GM1, were found to be intimately involved with cation binding. It is proposed that the higher affinity, compared with monomeric sialic acid, of GM1 for cations may result from these additional oligosaccharide groups, which may effectively compete for water ligands in the metal cation coordination sphere.

Ceramides↗
PubMed1978

Ganglioside alterations in guinea pig brains at end stages of experimental Creutzfeldt-Jakob disease.

Gangliosides were isolated from guinea pig brains at the end stages of experimental Creutzfeldt-Jakob disease. Quantitative analyses revealed marked decreases of ganglioside levels in pathologically devastated tissues such as cerebral cortex (-21%), basal ganglia and thalamus (-18%), and brain stem (-23%). The cerebellum revealed only minor pathological abnormalities and its ganglioside level remained unchanged. Thin-layer chromatography of the Creutzfeldt-Jakob brain gangliosides showed aberrant ganglioside patterns in all regions studied, including the cerebellum. With some exceptions, a trend in ganglioside pattern changes was detected which consisted of proliferation of GM3, GD3, GD2 and loss of GM1, GD1a, GD1b and GT1b.

Animals↗
PubMed1978

Isolation and characterization of human liver hematoside.

The monosialoganglioside hematoside (GM3) is an important precursor in the synthesis of the more complex gangliosides. To obtain large quantities of GM3 for use in ganglioside biosynthetic experiments, we have devised a column chromatographic procedure for the isolation and purification of GM3 from human liver. A total ganglioside mixture was obtained from a 550 g sample of normal human liver. Quantitative analysis by gas-liquid chromatography indicated about 66 microgram of lipid-bound N-acetylneuraminic acid per gram of fresh tissue. Hematoside appeared as double bands on thin-layer plates and represented 86.4% of the total sialic acid content. Additional ganglioside species, notably GD3, were also seen. Hematoside was separated from the other gangliosides by GM3 obtained was 120 mg, which represented a 90% recovery. Although the long-chain base and sugar compositions of the upper and lower GM3 fractions were similar, striking fatty acid differences were detected. The upper fraction contained predominantly unsubstituted fatty acids, while the lower fraction showed a preponderance of alpha-hydroxy fatty acids. The unsubstituted fatty acid and hydroxy fatty acid composition of the total GM3 fraction was calculated to be 56.9% and 43.1%, respectively.

Chromatography, Gas↗
PubMed1978

Gangliosides of human, cat, and rabbit spinal cords and cord myelin.

Gangliosides were isolated from whole spinal cords and cord myelin of human, cat, and rabbit by a revised methodology. The method included the sequential application of DEAE-Sephadex column chromatography, base treatment, Sephadex G-50 column chromatography, and finally Iatrobeads column chromatography. The human whole spinal cord was found to contain about one-tenth of the ganglioside concentration as in cerebral gray matter and about one-third of that in cerebral white matter. Low levels of gangliosides were also found in cat and rabbit whole cords. Only N-acetyl neuraminic acid could be detected in the ganglioside fractions of all three species. The whole cords also possessed unique ganglioside patterns when compared with the patterns of cerebral tissues. The most prominent and consistent features were the reduced concentration of Gd1a and increased amounts of Gm3 and Gd3. Human, but not cat and rabbit, spinal cord also contained Gm4 as one of the major gangliosides. Myelin prepared from the spinal cords of all three species also contained gangliosides. The amounts were only about half of those in the respective cerebral white matter myelin. The cord myelin ganglioside pattern was generally similar to the cerebral white matter myelin within the same species. Gm1 was the most abundant ganglioside in the cord myelin. Gm4 was found to be highly enriched only in myelin prepared from human sources.

Animals↗
PubMed1977

Isolation and characterization of a novel trisialoganglioside, GT1a, from human brain.

A novel trisialoganglioside has been isolated from normal adult human brain in a yield of 0.6% of the total gangkioside. By graded neuraminidase treatment, mild acid hydrolysis and periodate oxidation analysis, the ganglioside was identified as GT1a having the following structure: NeuAc(alpha, 2-8)NeuAc(alpha, 2-3)Gal(beta, 1-3)GalNAc(beta, 1-4) [NeuAc(alpha, 2-3)]Gal(beta, 1-4)Glc(1-1)ceramide.

Brain Chemistry↗
PubMed1977

Ganglioside content and pattern in human gliomas in culture. Correlation of morphological changes with altered gangliosides.

The ganglioside level and pattern of human gliomas in monolayer cultures were examined. These gliomas revealed morphological variations that correlated with several features of ganglioside analysis. Glioblastoma lines TC 178 and TC 501 that morphologically had changed during extended subculture revealed reduced amounts and a simplified pattern of gangliosides with almost total loss of the characteristic brain complex gangliosides. In contrast, two glioblastoma lines TC 526 and TC 593, as well as the oligodendroglioma line TC 620 showed brain-like gangliosides and the cells in these cultures had maintained their characteristic morphology observed during early subcultures. The possibility that altered ganglioside levels occur in conjunction with morphological changes after propagation in vitro is discussed.

Brain Neoplasms↗
PubMed1977

Influence of trichloroacetic acid-phosphotungstic acid on the thin layer chromatographic mobility of gangliosides.

Trichloroacetic acid (TCA)-phosphotungstic acid (PTA) precipitation has been used as a faster procedure than dialysis for the isolation of gangliosides, but the TCA-PTA treatment causes striking abnormalities in the thin layer chromatographic mobilities of the gangliosides. However, a normal chromatographic pattern can be restored by treating the precipitated gangliosides with the tetrasodium salt of ethylenediamine tetraacetic acid followed by dialysis. Hence, TCA-PTA treatment does not appear to cause artifacts or hydrolysis of the gangliosides.

Brain Chemistry↗
PubMed1977

A Waldenström macroglobulin that is both a cold agglutinin and a cryoglobulin because it binds N-acetylneuraminosyl residues.

A purified human monoclonal IgM(kappa) (cold agglutinin MKV) has been characterized as both a cold agglutinin and a cryoglobulin. Since its reactivity with human erythrocytes but not with dog erythrocytes is reduced by treatment of the cells with ficin and its reactivity with both is abolished by treatment of the cells with neuraminidase, it has by definition Pr(2) specificity [Roelcke, D. (1974) Clin. Immunol. Immunopath. 2, 266-280]. Presumably, the membrane receptors for cold agglutinin MKV are sialic acid-containing glycoproteins in human cells and sialic acid-containing glycolipids in dog cells. Agglutination of erythrocytes is specifically inhibited by II(3)-N-acetylneuraminosyllactosylceramide (GM(3)) and N-acetylneuraminosylparagloboside but not by their N-glycolylneuraminosyl forms or by lactosylceramide or paragloboside, and the reactivity of neuraminidase-treated cells can be restored by allowing them to absorb either GM(3) or N-acetylneuraminosylparagloboside. When large amounts of ganglioside are absorbed, the cells are agglutinated not only in the cold, but also at 37 degrees , showing that the density of receptor sites on the erythrocyte surface can influence the thermal amplitude of cold agglutinins. Liberation of sialic acid from cold agglutinin MKV by treatment with neuraminidase (acylneuraminosyl hydrolase; EC 3.2.1.18) does not affect its agglutinating properties but the asialoprotein is no longer a cryoglobulin. Apparently the physical basis for its precipitation in the cold is the intermolecular immune binding of N-acetylneuraminosyl residues.

Adult↗
PubMed1976

In vitro biosynthesis of sialosylgalactosylceramide (G7) by mouse brain microsomes.

A sialytransferase activity which catalyzes the synthesis of sialosylgalactosylceramide (G7) from added galactocerebroside and CMP-N-acetylneuraminic acid has been demonstrated in mouse brain microsomes. The enzyme reaction shows a pH optimum of 6.3 and requires detergents. Both Mn2+ and Ca2+ inhibited the reaction, whereas Mg2+ had no effect. The apparent Km for galactocerebroside leading to G7 was estimated to be 8.7 X 10(-4) M. The same microsomal preparation also synthesized hematoside when ceramide lactoside was the glycolipid acceptor. The apparent Km for ceramide lactoside was about one-tenth that for galactocerebroside. When the preparations were partially inactivated by heat the synthesis of G7 and of hematoside was reduced at approximately the same rate. Liver appeared to have the highest activity for G7 synthesis (as well as of hematoside), followed by brain. The synthesis of B7 by mouse brain microsomes in vitro demonstrates a new pathway for brain ganglioside synthesis.

Animals↗