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R K Yu

Publications and source records attributed to R K Yu.

At least 235 records · Page 13Linked to original sources
PubMed1982

Retinal gangliosides in RCS mutant rats.

The distribution of retinal gangliosides was studied in normal and mutant rats with retinal dystrophy at 30 and 180 days of age. The loss of photoreceptor cells in the retinal dystrophic RCS rats was not associated with a significant reduction in the relative distribution of any of the major retinal gangliosides. The loss of photoreceptors, however, caused a marked increase in total retinal ganglioside concentration. These findings suggest that photoreceptor cells contain a low concentration of gangliosides and that no major retinal ganglioside is localized or concentrated in these cells. The cellular localization and function of the most abundant retinal ganglioside, GD3, is discussed.

Aging↗
PubMed1982

Myelin gangliosides in vertebrates.

A phylogenetic survey of brain myelin ganglioside patterns and concentrations has been carried out on 16 vertebrate species. Gangliosides were isolated from purified myelin and found to vary in concentration from 25 micrograms of sialic acid per 100 mg of myelin for goldfish to a value of 395 for turkey. The latter species had approximately equivalent amounts of GM1 and GM4 as the two major gangliosides. The 11 mammals studied all had GM1 as the major ganglioside, with variable amounts of GM4; rhesus monkey and human had 20-25% GM4, whereas the others had less than 10%. Amphibia and fish myelin contained the least total ganglioside, with patterns that showed relatively little GM1 and no detectable GM4. Alligator myelin was unique in having a total concentration as high as the avian species, but a pattern with predominantly di- and trisialo gangliosides.

Aged↗
PubMed1982

Characterization of GM1 ganglioside by direct inlet chemical ionization mass spectrometry.

Intact permethylated and permethylated-reduced (LiAlH4) derivatives of GM1 ganglioside were analyzed by direct inlet ammonia chemical ionization (CI) mass spectrometry. In addition, the trimethylsilylated derivative of the permethylated-reduced sample of this ganglioside was similarly analyzed. CI mass spectrometry proves to be a highly satisfactory method for structural studies of GM1 ganglioside because of the simple fragmentation pattern and the presence of prominent molecular ions and fragment ions in the high mass region. Complete information on the carbohydrate sequence and lipophilic composition can be easily obtained.

Animals↗
PubMed1981

Observation by 13C NMR of interactions between cholera toxin and the oligosaccharide of ganglioside GM1.

The initial event in the action of cholera toxin on intact cells is its recognition of cell-surface receptors, molecules of ganglioside GM1. We have studied details of this interaction by 13C NMR, which enables us to examine simultaneously both the protein and the ganglioside or, as in the present instance, its oligosaccharide portion. 13C NMR spectra of the toxin are consistent with the long correlation times expected for this 84,000-dalton protein. They show, however, some resolved resonances (including one tentatively assigned to the epsilon 2 carbon of tryptophan, 138.3 ppm downfield from tetramethylsilane). When oligosaccharide is added to the toxin this resonance broadens or moves further upfield to reside under phenylalanine resonances at 136.7 ppm. Of the seven tryptophan residues in cholera toxin, five are in the B subunits which bind GM1, so that the data are consistent with a resonance shift for the epsilon 2 carbons of these residues on binding the oligosaccharide. Resonances arising from the anomeric and methylene carbons of the sialic acid moiety of the oligosaccharide are also shifted. Comparison with corresponding chemical shifts in a series of model compounds suggest that the latter effects may originate in a toxin-induced conformational change in the oligosaccharide. At high resolution, anomeric carbon resonances of terminal galactose residues in free and bound oligosaccharide are also resolved.

Carbohydrate Conformation↗
PubMed1981

Isolation and characterization of a novel monosialosylpentahexosyl ceramide from Tay-Sachs brain.

A novel monosialoganglioside was isolated from Tay-Sachs brains. It represented about 0.1% of the total ganglioside mixture. Compositional analysis by gas-liquid chromatography indicated that it contained glucose, galactose, N-acetylgalactosamine, N-acetylneuraminic acid, and long chain base in the molar ratio of 1:2:2:1:1. The ganglioside was found to be resistant to neuraminidase (Clostridium perfringens), beta-hexosaminidase (jack bean), and beta-galactosidase. However, it could be degraded by a human liver beta-hexosaminidase preparation in the presence of an activator to produce a glycolipid chromatographically identical with authentic IV3NeuAc-GgOse4-ceramide. This glycolipid product was resistant to beta-galactosidase (jack bean), but could be readily degraded to GgOse4-ceramide by neuraminidase. Mild formic acid hydrolysis degraded the intact ganglioside to an asialo derivative chromatographically identical with the pentahexosyl ceramide (GalNAc-Gal-GalNAc-Gal-Glc-ceramide) derived from GD1a-GalNAc. The asialo derivative could then be degraded to GgOse4-ceramide and GgOse3-ceramide by sequential treatment with jack bean beta-hexosaminidase and beta-galactosidase. These data suggest that the novel ganglioside is a monosialosylpentahexosyl ceramide with the sialosyl group attached to the penultimate galactose moiety of the pentahexosyl ceramide backbone, and it has the following structure: GalNAc(beta 1-4)Gal(beta 1-3)GalNAc(beta 1-4)Gal(beta 1-4)Glc-ceramide (formula see text).

Brain Chemistry↗
PubMed1981

Abnormal maturation of cerebral cortex and behavioral deficit in adult rats after neonatal administration of antibodies to ganglioside.

Five-day-old rats received a single injection (50 microliter) of antiserum to ganglioside into the cisterna magna and were compared to control animals injected with the antiserum which had been absorbed with pure GM1 ganglioside to remove the specific antibodies. Both groups showed normal rates of body growth. However, animals receiving antiganglioside serum had, at 60 days of age, impaired performance when tested on a complex learning task (DRL) as well as chemical and morphological alterations in the somatosensory cerebral cortex. Gross morphology and wet weight of whole brain were normal in both groups. Microchemical analysis of somatosensory isocortex revealed a normal content of total solids, protein, and DNA. However, ganglioside sialic acid, galactocerebroside, and RNA were decreased by 31%, 32% and 25% of control values, respectively (P less than 0.01). Quantitative measurements of oblique dendrites of Golgi-stained cortical pyramidal neurons revealed a 31% decrease in the number of spines. Additionally, the majority of spines were of the stubby configuration, whereas dendrites from controls were populated predominately by thin spines. These observations suggest that antibodies to GM1 ganglioside interfere with optimal neonatal development on both dendrites and myelin in cerebral cortex. The results provide an animal model in which an immunologically-mediated disturbance of cortical development is associated with chronic behavioral impairment.

Animals↗
PubMed1981

Myelin gangliosides: an unusual pattern in the avian central nervous system.

Gangliosides were isolated from purified myelin obtained from brain and spinal cord of mature chickens and pigeons. Total concentrations were approximately two- to fivefold greater than for previously reported mammalian species, and their patterns also differed in containing significantly more sialosylgalactosylceramide (GM4). The latter comprised one-third to one-fourth of total myelin ganglioside, approximately equivalent to GM1 (II3NeuNAcGgOse4Cer). As in mammals, GM4 of avian CNS appeared to be localized in myelin. Fatty acids of this ganglioside included both the hydroxy- and unsubstituted types, and long-chain bases were almost entirely C18. Ganglioside GM1 split into two closely migrating bands on TLC, the slower of which resembled mammalian GM1 in having stearate as the main fatty acid with a measurable amount (10%) of C20-sphingosine; the faster band had predominantly longer-chain fatty acids and very little C20-sphingosine.

Animals↗
PubMed1980

In vitro biosynthesis of an isomer of brain trisialoganglioside, GT1a.

A sialyltransferase activity which catalyzes the synthesis of the trisialoganglioside GT1a from added disialoganglioside TD1a and CMP-N-acetylneuraminic acid has been demonstrated using a particulate fraction of 9-day-old embryonic chick brains. The enzyme exhibited optimum activity with the detergent Triton CF-54 and showed a broad pH optimum of 6.0 to 7.2. Ca2+ inhibited the reaction, whereas Mn2+, Mg2+, and EDTA had no effect. Slight elevations in activity were seen in the presence of Hg2+ or histone. The apparent Km for GD1a leading to GT1a was estimated to be 10(-3) M. When the monosialoganglioside, GM1, was used as the glycolipid substrate under conditions optimum for the synthesis of GR1a from GD1a, approximately 65% of the radioactive label was found in GD1a. However, about 50% of the remaining radioactivity was found in GT1a. The results suggest that the synthesis of GR1a could proceed via the sequence GM1 yields GD1a yields GT1a.

Animals↗
PubMed1980

Structures of some new complex gangliosides of fish brain.

Three novel trisialogangliosides of fish brain, GT3, GT2 and GT1c, have been isolated in their intact forms and their structures characterized. The discovery of these ganglioside species provides essential links for a new possible biosynthetic pathway leading to the major tetrasialoganglioside, GQ1c, of the fish brain.

Animals↗
PubMed1980

Heterosis for brain myelin content in mice.

Biochemical evidence of heterosis (hybrid vigor) for brain myelin content is presented. The concentrations of cerebroside and GM1 ganglioside, two glycolipids known to be abundant in myelin, were higher in the brains of (C57BL/6J X DBA/2J) F1 hybrids than in the brains of either parental strain. Furthermore, brain water content, which is known to be inversely related to myelin content, was lower in the F1 hybrids, especially during the most active period of myelin synthesis. Heterosis was not observed, however, for total brain ganglioside concentration. Additionally, the results do not substantiate a direct developmental-genetic relationship between brain myelin content and susceptibility to audiogenic seizures.

Animals↗
PubMed1980

Genetic analysis of audiogenic seizure susceptibility in C57BL/6J X DBA/2J recombinant inbred strains of mice.

The inheritance of susceptibility to audiogenic seizures (ASs) was studied in the C57BL/6J (B6) and DBA/2J (D2) progenitor strains, their reciprocal F(1) hybrids, backcross generations and in 21 B6 x D2 recombinant inbred (RI) strains of mice at 21 days of age. All of the D2 mice tested experienced ASs, whereas none of the B6 mice responded to the sound. Although 23% of the F(1) mice experienced wild running, they were generally as resistant to ASs as their B6 parents. Mice of the F(1)x B6 backcross generation were also resistant to ASs. In the F(1)x D2 backcross generation, however, a significant preponderance (72%) of AS-susceptible mice was found. No significant association was observed between any of the four coat-color phenotypes that were segregating in this generation and susceptibility to ASs. A continuous distribution of mean seizure severity scores and several new audiogenic response phenotypes, distinctly different from the phenotypes of either progenitor strain, were found among the 21 RI strains. These and the results from the F(1)x D2 backcross generation suggest that the difference in AS susceptibility between 21-day-old B6 and D2 mice cannot be under the control of a single locus. In addition, no association was found between AS susceptibility and the chromosome 4 markers Lyb-2, Mup-1 and b among the 21 RI strains. An association was observed, however, between AS susceptibility and the Ah locus. Several of the RI strains that were AS resistant at 21 days of age became AS susceptible as adults. One RI strain was susceptible to ASs at both young and adult ages. The B6, D2 and F(1) mice were completely resistant to ASs at adult ages. Genetic differences were found among the RI strains for the incidence, onset, duration, and type of severity of ASs. A remarkable amount of phenotypic variability in the audiogenic response, which can be attributed only to the influence of environmental factors, occurred within several of the RI strains. A multiple-factor mode of inheritance involving a physiological threshold can account for our observations.

Acoustic Stimulation↗