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R K Yu

Publications and source records attributed to R K Yu.

At least 163 records · Page 9Linked to original sources
PubMed1987

A human IgM M-protein in a patient with unknown bleeding disorder binds to beta-galactosyl and beta-glucosyl residues.

In a patient with an unknown bleeding disorder and an IgM lambda paraproteinemia, we demonstrated by thin-layer chromatography immunostaining and enzyme-linked immunosorbent assay that this protein specifically bound to a number of glycolipids and glycoproteins which have terminal beta-galactosyl or beta-glucosyl residues. Binding to galactosylceramide or glucosylceramide was inhibited by both galactosylceramide and glucosylceramide. From these studies, it is apparent that the M-protein recognized both beta-galactosyl and beta-glucosyl residues. This M-protein was also shown to prolong the partial thromboplastin time of normal plasma. Thus, this case represents an example of anti-carbohydrate specificity of an IgM M-protein in association with a spontaneous bleeding disorder.

Carbohydrate Conformation↗
PubMed1987

An immunosuppressive factor interacts with membrane glycolipid asialo-GM1 structure.

An immunosuppressive factor was isolated from sheep-erythrocyte hyperimmunized mouse serum. Possibilities of the adsorption of the immunosuppressive factor with glycolipid asialo-GM1 incorporated liposome (dipalmitoyl lecithin) and the blockade of immunosuppressive activity by specific anti-asialo-GM1 incorporated antibody were tested. We report here that: The immunosuppressive activity of the immunosuppressive factor decreased quantitatively if the factor was preincubated with asialo-GM1 incorporated liposome (GALP) as compared with that preincubated with liposome (LP) alone; and the presence of specific anti-asialo-GM1 antibody is able to protect in vitro anti-sheep erythrocyte (SRBC) response from the suppressive effect of the immunosuppressive factor in a dose-dependent fashion under similar cell culture condition. The results indicate that asialo-GM1 may be related to the receptor of immunosuppressive factor.

Animals↗
PubMed1987

Subcellular localization of sulfated glucuronic acid-containing glycolipids reacting with anti-myelin-associated glycoprotein antibody.

Peripheral nerve glycolipids, with which anti-myelin-associated glycoprotein (MAG) antibodies from patients with demyelinating neuropathy and plasma cell dyscrasia cross-react, proved to be novel glycosphingolipids containing a sulfated glucuronyl residue. Consequently, there has been much interest in the immunological role that these sulfated glucuronyl-glycosphingolipids (SGGLs) may play in the pathogenesis of this disorder. For the determination of the distribution of these glycolipids in various nervous tissues and, thereby, the elucidation of their pathogenicity, a quantitative immunostaining-TLC method for their detection has been devised. Using this method, we demonstrated that these glycolipids were distributed in greatly different amounts in the peripheral nerves from human, bovine, chicken, rat, and rabbit. Subcellular localization studies of bovine peripheral nerve also demonstrated that they were enriched in the axolemma-enriched fraction and present in glial-related membranes in lower concentrations. In addition, these glycolipids were present in bovine dura mater and transformed rat Schwann cells. These biochemical results suggest that not only myelin but also axons could be involved as targets of the anti-MAG antibody in macroglobulinemia neuropathy, and it may also be necessary to examine anti-SGGL activity in patients with axonal neuropathy associated with plasma cell dyscrasia.

Animals↗
PubMed1987

Myelin galactolipid synthesis in different strains of mice.

Previous studies have indicated that the brains of DBA/2J (D2) mice have a more heavily myelinated CNS than those of C57BL/6J (B6) at postnatal days 17-21. However, the amount of myelin in the brains of F1 (B6 X D2) hybrids is even higher than in their parental strains. To investigate further factors involved in regulating myelinogenesis in these mice, we have focused on the synthesis of cerebrosides and sulfatides, galactolipids enriched in myelin. Brain slices from 14-, 17-, and 21-day-old D2, B6, and F1 mice were incubated with [3H]galactose and [35S]sulfate. After incubation, microsomes, myelin, and oligodendroglial cells were isolated, and the galactolipids were analyzed. At 21 days of age, the labeling of cerebrosides in F1 mice was higher than in D2 and B6 mice when the results were expressed as microsomal or myelin radioactivity per gram wet weight. At 14 and 17 days of age, the labeling of cerebrosides in F1 animals was similar to that in D2 mice and was considerably higher than that in B6 mice. The labeling of sulfatides in F1 animals was significantly higher than in the B6 parent at all ages studied, whereas it remained higher than that in the D2 parent only at 17 days of age. A similar relationship among the strains was observed when the synthesis of myelin galactolipids was estimated by measuring the in vitro activity of UDP-galactose:ceramide galactosyltransferase and 3'-phosphoadenylyl sulfate:galactosylceramide 3'-sulfotransferase. The results indicate that the increased accumulation of myelin galactolipids previously reported in the F1 mice is partially due to enhanced synthetic activity.

Aging↗
PubMed1987

Localization of glycoconjugates recognized by the HNK-1 antibody in mouse and chick embryos during early neural development.

The monoclonal antibody HNK-1 recognizes a carbohydrate epitope present on a host of glycoconjugates which include the glycoproteins neural cell adhesion molecules (N-CAM) myelin-associated glycoprotein and ependymins, and two glycolipids. Other antibodies, including NC-1, L2 and IgM paraproteins from neuropathy patients share similar binding specificity to the same or related sulfated glucuronyl-containing antigen (SGA). To further investigate its possible significance in early development, the distribution of SGA was studied in the head region of early developing chick (S13-S18) and mouse (E8.5-E11.5) embryos by immunocytochemistry. A striking species difference was found in the apparent distribution of immunodetectable SGA. In chick, migrating neural crest cells and their related cell types were heavily stained by HNK-1; whereas no stain was detectable on mouse neural crest cells at comparable stages, except perhaps in a restricted area adjacent to the otic placode and immediately adjacent to the neural tube. Within the developing CNS, the distribution of SGA was similar in both species. It was first expressed on neuroepithelial cells prior to axonal outgrowth, and was distributed in a continuous zone along the entire lateral walls of the early neural tube. Little or no SGA was detectable along most of the floor and roof plates. SGA appeared during this same period in the lateral basal lamina and within the adjacent mesenchyme and nearby cells. SGA was particularly evident on neuroepithelial endfeet at this stage. Early developing longitudinal axons were subsequently found to grow in association with the endfeet of SGA-positive neuroepithelial cells. These findings, in conjunction with previous studies, suggest that SGA is associated as a marker, and perhaps functionally, with the organization of early neuronal settling and axonal growth patterns within the developing vertebrate CNS.

Animals↗
PubMed1987

Neuropathy and IgM paraproteinemia: differential binding of IgM M-proteins to peripheral nerve glycolipids.

Two patients with neuropathy and IgM paraproteinemia displayed different immunoreactivity to acidic peripheral nerve glycolipids. In one patient, immunostaining on thin-layer chromatographic plate revealed binding of the IgM to sulfated glucuronosyl paragloboside (SGPG) and sulfated glucuronosyl lactosaminyl paragloboside (SGLPG). The other IgM bound SGPG, SGLPG, and a new third glycolipid. Immunoreactivity of the IgM varies in this syndrome.

Aged↗
PubMed1987

Isolation and characterization of ganglioside GM1b from normal human brain.

A sialidase-susceptible monosialoganglioside was isolated from normal human brain by DEAE-Sephadex A-25 and Iatrobeads column chromatography. The yield of this ganglioside was about 6 mg per whole brain. Its structure was elucidated by sugar analysis, sialidase digestion, permethylation, and proton NMR studies. This ganglioside had carbohydrate, fatty acid, and long-chain base compositions identical to those of brain GM1a. However, the sialosyl residue was found to be linked (alpha 2-3) to the terminal galactosyl residue of the asialo-GM1a backbone. The complete structure of this ganglioside was therefore identified as GM1b or IV3NeuAcGgOse4Cer.

Adult↗
PubMed1986

Elucidation of glycolipid structure by proton nuclear magnetic resonance spectroscopy.

The primary structure of the oligosaccharide moiety of a glycosphingolipid can be elucidated by employing high-field proton nuclear magnetic resonance (NMR) spectroscopy. Information with respect to the composition and configuration of its sugar residues, and the sequence and linkage sites of the oligosaccharide chain can be obtained by employing a variety of one- and two-dimensional techniques. The latter include both scalar and dipolar correlated two-dimensional NMR spectroscopy. These techniques are also useful in establishing the solution conformation (secondary structure) of the oligosaccharide moiety. Examples in utilizing these techniques in elucidating the primary and secondary structures of glycolipids are presented.

Carbohydrate Conformation↗
PubMed1986

Molecular interactions and thermotropic behavior of glycosphingolipids in model membrane systems.

The oligosaccharide chain of glycosphingolipids (GSLs) has a marked influence on their thermotropic behavior, intermolecular packing and surface electrical potential. The transition temperature and enthalpy of GSLs decrease proportionally to the complexity of the polar head group and show a linear dependence with the intermolecular spacings. Interactions occurring among GSLs and phospholipids induce changes of the molecular area and surface potential that depend on the type of GSLs. Increasing proportions of phospholipids perturb the thermodynamic properties of the GSLs up to a point where phase separated phospholipid domains separate out but no phase separation of pure GSLs occurs. Heterogeneous equilibria among different structures occur for some systems. Large changes of the molecular free energy, eccentricity, asymmetry ratio and phase state of the GSLs-containing structure can be triggered by small changes of the molecular parameters, lipid composition and lateral surface pressure. The thermotropic behavior of GSLs is considerably perturbed by myelin basic protein. Phase separation occurs depending on the amount of protein and type of GSLs. The protein induces a decrease of the lipid molecular area, the more so the more complex the oligosaccharide chain in the GSLs. These membrane systems can not be described only on the basis of the individual properties of the molecules involved in a simple causal manner. Still scarcely explored long range thermodynamic, geometric and field effects that belong simultaneously to the intervening molecules, to the morphological properties of the structure involved and to the aqueous environment, are important determinants of their behavior.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1986

1H-2D-nuclear magnetic resonance applied to the primary structure determination of a novel octasaccharide glycolipid isolated from the spermatozoa of bivalves.

High resolution, two-dimensional 1H-n.m.r. spectroscopy has been used to confirm a proposed primary structure of a glycolipid having an octasaccharide head-group. Pure absorption and relay experiments were found to be particularly useful in establishing connectivities in poorly resolved regions of the spectrum. The spectral assignments, which indicate novel linkages including an internal fucopyranosyl residue as well as terminal xylosyl and 4-O-methylglucopyranosyluronic acid groups, add to a growing data base for structural characterization through n.m.r. spectroscopy.

Animals↗
PubMed1986

Immunocytochemical localization of GD3 ganglioside to astrocytes in murine cerebellar mutants.

Biochemical analysis of the murine mutants, Purkinje cell degeneration (pcd/pcd), staggerer (sg/sg) and lurcher (Lc/+), which are characterized by neuronal degeneration in the cerebellar cortex, have revealed substantially elevated levels of GD3 ganglioside (ceramide-Glu-Gal-NANA-NANA). Ultrastructural studies on pcd/pcd and sg/sg have shown astrocytes elaborating slender sheet-like processes which wrap around neuronal processes. Seyfried et al. hypothesized that the elevation in GD3 seen in these mutants is attributed to its expression by altered astrocytes. Using a monoclonal antibody to GD3 and a polyclonal antibody to GFAP we have explored the cellular localization of GD3. Positive immunofluorescence was observed in sg/sg, pcd/pcd and Lc/+ cerebella, but not in age-matched normal littermates or in weaver (wv/wv) a fourth cerebellar murine mutation which destroys granule cells prior to their migration across the molecular layer. In wv/wv cerebella, astrocytes do not elaborate sheets of processes and no significant elevations of GD3 are observed biochemically. The positive GD3 staining in pcd/pcd and Lc/+ was confined to the granule cell layer and appeared as many punctate or short, fine profiles, suggestive of binding to thin cytoplasmic processes. No GD3 positive staining was seen in the Bergmann glia or astrocytes of the white matter. GD3-positive staining was seen throughout the cortex in sg/sg which displayed severe disruption of its histoarchitecture with no clear delineation between the molecular and granule cell layers. Ultrastructural localization of GD3 was performed using pre-embedding immunocytochemistry with a PAP technique in sg/sg mice. The cytoplasmic processes and cell bodies of astrocytes displayed positive membrane staining. Our results suggest that astrocytes undergo important changes in membrane composition during pathological reaction caused by neuronal degeneration.

Animals↗
PubMed1986

1H-NMR assignments of GM1-oligosaccharide in deuterated water at 500 MHz by two-dimensional spin-echo J-correlated spectroscopy.

The 1H-NMR spectra of the oligosaccharide derived from monosialoganglioside GM1 (GM1 = beta-D-galactosyl-(1-3)-beta-D-N-acetylgalactosaminyl-(1-4)- [alpha-N-acetylneuraminyl-(2-3)-]-beta-D-galactosyl-(1-4)-b eta-D-glucosylceramide) (GM1OS) and its reduced form (GM1OS-R) have been obtained at 500 MHz in D2O. Through the combined use of one-dimensional and homonuclear two-dimensional spin-echo J-correlated (2D SECSY) spectra of GM1OS-R, the assignments for the ring protons of GM1OS are made. Data on chemical shifts and coupling constants of GM1OS including the alpha-linked neuraminic acid protons, in aqueous solution, are tabulated. Due to the very small coupling constants (less than 2 Hz) and the closeness in chemical shifts (less than 0.04 ppm) for the pair of correlated peaks in the two-dimensional spectrum, the information on the connectivities of the H5 ring protons of the neutral sugar residues is missing. Second-order coupling also blurs this information. Data are compared with those obtained for ganglioside GM1 in dimethyl sulfoxide (DMSO; the actual composition therein was 97% DMSO-d6 and 3% D2O) by T. A. W. Koerner, J. H. Prestegard, P. C. Demou, and R. K. Yu (1983, Biochemistry 22, 2676). While the heterogeneity of chemical shifts for the H5, H6a, and H6b protons diminishes in D2O, that for A-9a and A-9b remains. The latter suggests an intraneuraminic acid conformation involving the glycerol side chain unaffected by the solvent. Moreover, the chemical shifts of the III-1, III-2, and A-4 protons (and perhaps the II-4, IV-2, and A-8 protons) in D2O exhibit unusual upfield shifts compared with those in DMSO. This indicates that the intramolecular interactions between GalNAc residue III and neuraminic acid present in DMSO are weakened in D2O. The effect of temperature on the conformation is also examined and appears to be minimal (less than 0.02 ppm) in the range 22-50 degrees C.

Animals↗
PubMed1986

Acidic lipids enhance cathepsin D cleavage of the myelin basic protein.

Some acidic lipids including sulfatide and phosphatidylinositol were found to increase greatly the rate of cathepsin D cleavage of the myelin basic protein. Since a similar effect was seen when the substrate was changed to cytochrome C, but not when the enzyme was changed to pepsin, these acidic lipids seem to be acting on cathepsin D rather than on myelin basic protein itself. Even so, chemical modification studies suggest that this phenomenon is only seen when the myelin basic protein is in its native conformation. Succinylation of MBP increases its rate of cleavage by cathepsin D by at least tenfold and, in addition, with this modified and presumably denatured MBP as substrate, activation of cathepsin D is no longer seen with acidic lipids. These findings suggest that the native conformation of MBP is both an important determinant of its rate of cleavage by cathepsin D and is also essential for observing activation of this reaction by acidic lipids. The acidic lipids seem to alter the "extended active site" of cathepsin D in such a way as to enable this enzyme better to utilize the native myelin basic protein as a substrate. Cathepsin D has previously been implicated as the protease responsible for the release into cerebrospinal fluid in multiple sclerosis patients of an encephalitogenic fragment derived from myelin basic protein. It is possible that the elevated levels of cathepsin D and sulfatide that have previously been found associated with multiple sclerosis plaques in vivo act in concert to bring about the rapid cleavage and subsequent loss of the myelin basic protein from these localized regions in the myelin sheath.

Animals↗
PubMed1986

Gangliosides inhibit phospholipid-sensitive Ca2+-dependent kinase phosphorylation of rat myelin basic proteins.

Gangliosides inhibit the phosphorylation of both small and large rat myelin basic proteins (SMBP, LMBP) by an endogenous phospholipid-sensitive Ca2+-dependent protein kinase (C-kinase). Using a rat brain myelin preparation in an in vitro phosphorylation assay system, we determined the inhibition constants (IC50's) of the gangliosides GM1, GD1a, GD1b, and GT1b to be approximately 160 microM, 65 microM, 65 microM, and 40 microM, respectively. Asialoganglioside GA1, ceramide, and N-acetylneuraminic acid (NANA, sialic acid) failed to produce similar inhibition, suggesting that both the lipid and the sialic acid moieties are necessary, but neither alone is sufficient to produce inhibition. The results indicate that gangliosides may regulate protein kinase C activities in the nervous system.

Animals↗
PubMed1986

Neuroimmunology of gangliosides in human neurons and glial cells in culture.

Gangliosides (sialic-acid-bearing glycolipids) have received attention in recent years because of their role in cell recognition phenomena, synaptic transmission, memory generation, and nerve regeneration in the fields of neurosciences. It is suggested that each brain region or each neural cell type may contain a specific and characteristic set of gangliosides. We have investigated the immunocytochemical localization of several classes of gangliosides that include GM1, GM4, GD3, and GQ gangliosides on the cell surface of various cell types found in human neural cell cultures with antibodies specific for these gangliosides. Cell cultures were obtained from adult human brains and fetal human dorsal root ganglia and spinal cord and cultured in vitro for the period up to 6 months and utilized for the ganglioside immunocytochemistry. It was demonstrated that GM1 ganglioside was present in all galactocerebroside-positive oligodendrocytes and most of glial fibrillary acid protein (GFAP)-positive astrocytes (80%), most of neurofilament-positive neurons (80%), 50-70% of Schwann cells, and 5-10% of fibronectin-positive fibroblasts; GM4 ganglioside could be detected in all oligodendrocytes, 80% of astrocytes, and 50% of Schwann cells, while no staining was found in neurons or fibroblasts; GD3 ganglioside was present in all oligodendrocytes and 5-10% of astrocytes but not in neurons, Schwann cells, or fibroblasts; and all of fetal CNS neurons and approximately 80-90% of fetal dorsal root ganglia (DRG) neurons and a small percentage of astrocytes (10-20% in fetal and less than 1% in adult astrocytes) was labeled by A2B5 antibody which is specific for GQ ganglioside, while this antibody did not stain cell surface of oligodendrocytes, Schwann cells, or fibroblasts. Three classes of gangliosides, GM1, GM4, and GD3 were found to be definite components of fetal and adult human oligodendroglial plasma membrane, while GM1 and GM4 gangliosides were detected on the surface of most astrocytes. Only a minor population of astrocytes from both fetal and adult human CNS contained GD3 and GQ gangliosides. Two classes of gangliosides, GM1 and GQ, were detected on the surface of fetal human neurons. More than half of fetal Schwann cells reacted to GM1 and GM4 antibodies but did not to GD3 or GQ antibodies. We recognized the presence of a specific and characteristic set of gangliosides on the cell surface of different human neural cell types and these findings should facilitate further investigation of the precise biological activity of these gangliosides.

Aged↗
PubMed1986

Developmental expression of myelin basic protein mRNA in a hypermyelinating mouse.

Polysomal poly (A)+ RNA and total cellular RNA were isolated from the brains of C57BL/6J (B6), DBA/2J (D2), and F1 hybrid mice. Both types of RNA were isolated at 9, 12, 16, 21, and 30 days of age. By using a 32P-labelled cDNA probe for myelin basic protein (MBP; pMBP-1) the amounts of RNA coding for MBP present in the three strains at each age were determined. For both the polysomal poly(A)+ and total cellular RNA the peak of MBP RNA accumulation was at about 16-18 days for all three strains. These results imply that the developmental pattern of MBP RNA synthesis for F1 mice is not shifted with respect to the parental strains. For the polysomal poly(A)+ RNA, F1 had the greatest amount of MBP mRNA, B6 the least, and D2 an intermediate amount. F1 again had the greatest amount of MBP RNA from the total cellular pool at all ages. However, B6 had a greater amount of MBP RNA in the total cellular RNA pool than did D2. This demonstrates elevated transcription of the MBP gene in the F1 or an increase in message stability in this strain. It also suggests some form of translational control for MBP RNA in the B6 strain. In addition a second species of MBP RNA was found in the total cellular RNA pool. This species is larger than the major polysomal RNA band and may be a nuclear precursor.

Aging↗
PubMed1986

Effect of antiglycolipid antisera on the lipid composition of cultured mouse spinal cords.

To examine the effect of antiglycolipid antibodies on demyelination, myelinated cultures of embryonic mouse spinal cords were treated by antigalactocerebroside (anti-GC), anti-GM1; and anti-GM4 antisera, and the lipid composition of the cultures were studied. The anti-GC antiserum-treated cultures, which exhibited severe morphologic signs of demyelination, revealed a significant reduction of cerebroside. The anti-GM4 or anti-GM1 antiserum-treated cultures, which exhibited mild degrees of demyelination, also had low contents of cerebroside. These results support our previous data showing that antiglycolipid antibodies cause demyelination in cultured mouse spinal cords, and suggest a possible role of myelin-specific glycolipids in the demyelination process.

Animals↗