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Biomedical subjects

S C Li

Publications and source records attributed to S C Li.

At least 217 records · Page 12Linked to original sources
PubMed1979

Carbon 13 NMR spectroscopy of a cerebroside. Proof of the beta-pyranosyl structure of D-glucosylceramide.

The first 13C nuclear magnetic resonance spectrum of a cerebroside is reported. All signals of D-glucosylceramide (I), the cerebroside from human Gaucher's diseased liver, have been assigned by comparison of their chemical shifts with those of model compounds. This data has been used to demonstrate for the first time directly: (a) that the glucosyl moiety must exist in the pyranoside ring form and have a beta anomeric linkage, and (b) that the fatty acyl composition of the aglycon is: alpha-hydroxy, 0%; saturated, 86 +/- 2%; unsaturated long chain, 14 +/- 2%; and unsaturated short chain, less than or equal to 2%. The use of 13C signal shifts in the delta 80 to 120 region (anomeric window) for the assignment of glycon anomeric and ring forms demonstrated herein should be applicable to other glycoconjugates.

Cerebrosides↗
PubMed1979

Isolation and characterization of a heptaglycosylceramide from bovine erythrocyte membranes.

A heptaglycosylceramide was isolated from bovine erythrocyte membranes. The structure was characterized to be Gal(alpha 1-3)Gal(beta 1-4)GlcNAc(beta1-3)Gal(beta 1-4)Glc-NAc(beta 1-4)al(beta 1-4)GlcCer. A hexaglycosylceramide that has the same sequence except for the terminal alpha-galactosyl unit has also been isolated. We have previously found that gangliosides isolated from bovine erythrocyte membranes contain a keratan sulfate type repeating unit --[3Gal(beta 1-4)-GlcNAc beta]--n. This study shows that the keratan sulfate type repeating unit is also present in the neutral glycosphingolipids of bovine erythrocyte membranes.

Animals↗
PubMed1978

Occurrence of glycosphingolipids in chicken egg yolk.

Chicken egg yolk was found to contain a unique glycosphingolipid pattern not seen in other types of tissue or cell. These glycosphingolipids were isolated in pure form and their structures established by sequential enzymic hydrolysis and permethylation analysis. The major gangliosides in chicken egg yolk are N-acetylneuraminosylgalactosylceramide, N-acetylneuraminosyl-lactosylceramide and di-N-acetylneuraminosyl-lactosylceramide. The only neutral glycosphingolipid found in chicken egg yolk is galactosylceramide.

Animals↗
PubMed1978

Characterization of gangliosides from bovine erythrocyte membranes.

Two glucosamine-containing gangliosides, sialosylhexaglycosylceramides, were isolated from bovine erythrocyte membranes. Both gangliosides were hydrolyzed by neuraminidase isolated from Clostridium perfringens to become neutral hexaglycosylceramides. Based on the results of sequential enzymatic hydrolysis and gas chromatography-mass spectrometric analyses of the methylated sugars, the structures of these two gangliosides were shown to be NeuAcalpha2 leads to 3Galbeta1 leads to 4GlcNAcbeta1 leads to 3Galbeta1 leads to 4GlcNAcbeta1 leads to 3Galbeta1 leads to 4Glc-ceramide and NeuGcalpha2 leads to 3Galbeta1 leads to 4GlcNAcbeta1 leads to 3Galbeta1 leads to 4GlcNAcbeta1 leads to 3Galbeta1 leads to 4Glc-ceramide, respectively. In addition, N-acetyl- and N-glycolylneuraminosyllacto-N-neotetraosylceramides, and N-acetyl- and N-glycolylneuraminosyllactosylceramides were also found in bovine erythrocytes. The predominant fatty acids in these two gangliosides were C 22:0 and C 24:0. C-18 sphingosine was the major base detected.

Animals↗
PubMed1978

Increased glycosphingolipid excretion associated with proteinuria.

The urine of patients with proteinuria of various etiologies was examined to determine if proteinuria alone was associated with significant glycosphingolipiduria. In all cases of proteinuria examined, the level of glycosphingolipids in the urine was found to be markedly elevated. There was no evidence of a glycosphingolipid storage disorder in any case. It was concluded that significant glycosphingolipiduria may occur in proteinuria as well as in the glycosphingolipid storage disorders.

Adolescent↗
PubMed1976

beta-Mannosidase from the mushroom Polyporus sulfureus.

beta-D-Mannosidase (EC 3.2.1.25), a useful tool for the structural studies of heterosaccharide chains, has been isolated in a highly purified form from the fruiting bodies of the mushroom Polyporus sulfureus. This mushroom is unique among reported sources of this enzyme in that it has the advantage of being almost free of alpha-mannosidase activity. The purification procedure involves ammonium sulfate fractionation followed by Sephadex G-100 filtration and chromatography on columns of DEAE-cellulose and hydroxylapatite. The final enzyme preparation gives essentially a single band on disc gel electrophoresis. The purified enzyme liberates the beta-D-mannopyranosyl unit from various natural substrates such as the core glycopeptide, Man(GlcNAc)2-Asn isolated from ovalbumin, from Taka-amylase A, and from human alpha1-acid glycoprotein. It also hydrolyzes (Man)2-GlcNAc from the urine of an alpha-mannosidosis patient, 1,4-D-mannobiose and mannotriose isolated from ivory nut mannan, 4-O-beta-D-mannopyranosyl-L-rhamnose, 6-O-beta-D-mannopyranosyl-D-galactose and 4-O-beta-D-mannopyranosyl-N-acetylglucosamine. The molecular weight of this enzyme is estimated to be about 64,000 by gel filtration. For p-nitrophenyl-beta-D-mannopyranoside, the pH optimum is between 2.4 and 3.4 and the Km is 1.6 mM.

Basidiomycota↗
PubMed1976

An activator stimulating the enzymic hydrolysis of sphingoglycolipids.

An activator stimulating the enzymic hydrolysis of sphingoglycolipids has been purified from human liver. The purity of the activator, as examined by disc gel electrophoresis, showed one major band stained with both amido black and periodate-Schiff reagent. Chemical analyses identify the activator as a glycoprotein. The physical properties of the activator are: heat-stable, nondialyzable; molecular weight, about 21,000; isoelectric point (pI), 4.1. The purified activator stimulates the hydrolysis of GM1 by beta-galactosidase, GM2 by beta-hexosaminidase, as well as ceramide trihexoside by alpha-galactosidase A or B. The hydrolysis by glycosidases depends upon the amount of activator added. An antibody against the activator was developed from rabbits. The specificity of the antibody to the activator has been established. The antibody was used to make the affinity column for isolation of the activator. It was also used to develop a sensitive immunodiffusion method to detect the activator.

Acetylglucosamine↗
PubMed1975

Isolation and characterization of jack bean beta-galactosidase.

A simple procedure has been devised to isolate beta-galactosidase from jack bean meal. The final preparation gives one major protein banc in disc gel electrophoresis. The substrate specificity of this enzyme toward some natural oligosaccharides, glycoproteins, and sphingoglycolipids has been examined in detail. Among three isomers of N-acetyllactosamine, Galbeta1leads to4GlcNAc; while Galbeta1leads to3GlcNAc was hydrolyzed very slowly. This property can be used to distinguish the galactose linkage in asialo-GM1 (Galbeta1leads to3GalNAcbeta1leads to4Galbeta1leads to4Glcleads toCer) and that in lacto-N-neotetraosylceramide (Galbeta1leads to4GlcNAcbeta1leads to 3Galbeta1leads to4Glcleads toCer). For hydrolyzing glycolipids, the effect of sodium taurodeoxycholate and sodium taurochenodeoxycholate on the rate of hydrolysis was carefully examined. This enzyme hydrolyzes lactosylceramide and asialo-GM1 faster than GM1. These results suggest that in addition to the type and linkage of the penultimate sugar unit, the sugar unit at the distal position of the saccharide chain also affects the hydrolysis rate. It also readily liberates 80% D-galactosyl units from asialo alpha1-acid glycoprotein. Escherichia coli beta-galactosidase on the other hand cannot hydrolyze asialo-alpha1-acid glycoprotein, lactosylceramide, GM1, asialo-GM1, and lacto-N-neotetraosylceramide. The molecular weight of this enzyme is about 75,000 and the isoelectric point is pH 8.0. With p-nitrophenyl beta-D-galactopyranoside as substrate, optimal activity occurs at pH 2.8 with glycine-HCl buffer and at pH 3.5 with citrate-phosphate buffer. With lactose as substrate, the pH optimum in these two buffers are 2.8 and 4.0, respectively. Km values for p-nitrophenyl beta-D-galactopyranoside, o-nitrophenyl beta-D-galactopyranoside and lactose are 0.51 mM, 0.63 mM, and 12.23 mM, respectively. Many inhibitors for this enzyme including inorganic ions, monosaccharides, and glycosides are investigated. In contrast to E. coli beta-galactosidase, jack bean beta-galactosidase is not inhibited by p-aminophenyl thio-beta-D-galactopyranoside.

Carbohydrates↗
PubMed1975

Characterization of dog small intestinal fucolipids with human blood group H activity.

Fucolipids with human blood group H activity were isolated from several dog small intestines. On the basis of mass spectrometry, periodate oxidation, enzyme degradation, methylation, and immunologic studies the following structure is proposed: Fucalpha(1 yields2)Galbeta(1 yields 4)Glc-NAcbeta(1 yields 3)Galbeta(1 yields 4)Glc-ceramide. The ceramide was shown by mass spectrometry to contain hydroxyhexadecanoic acid and phytosphingosine as major consitutuents.

ABO Blood-Group System↗
PubMed1975

Characterization of human alpha-galactosidase A and B before and after neuraminidase treatment.

It has been previously reported that following neuraminidase treatment alpha-galactosidase A is converted into the B form, as revealed by electrophoresis. By a variety of techniques such as isoelectrofocusing, DEAE-chromatography and by enzyme kinetic parameters, no conversion of alpha-galactosidase A into B, or the reverse, could be detected after neuraminidase treatment. Only an apparent transformation of alpha-galactosidase A into B was revealed by Cellogel electrophoresis. In addition, a discrepancy was noticed between the pattern of electrophoretic migration on starch gel and Cellogel and the net electrical charges of the two alpha-galactosidases as deduced by isoelectrofocusing and DEAE-cellulose. Neuraminidase treatment did not affect the activity of alpha-galactosidase A towards the natural substrate, ceramidetrihexoside, but the activity of alpha-galactosidase B decreased by about 30% under the same conditions. The two forms of alpha-galactosidases A and B used in this study were extensively purified by classical procedures.

Animals↗
PubMed1975

Protein deficiency in primates. IV. Pregnant rhesus monkey.

Young adult female rhesus monkeys, maintained in a seminatural environment, when pregnant 30 days were fed a balanced semisynthetic diet containing 15.3 percent casein (13.4 percent protein) or 0.5, or 0.25 that amount for the remainder of thir pregnancy. The diets, made isocaloric by the addition of carbohydrates to replace the missing casein, supplied 4, 2, or 1 g protein/kg per day if the animals ate 120 kcal/kg per day, an assumption that was reasonably accurate. We studied the responses of monkeys delivering normal young at term. All monkeys were clinically healthy during the experiment. All reduced their total plasma protein concentration, principally by decreasing their albumin concentration. Greatest loss occurred in the low-protein group. Albuminuria was a common finding in all groups. Food consumption though varying throughout pregnancy, remained fairly comparable from group to group. Weight gain of the highest protein group was greatest; that for the lowest protein group barely covered the weight of the products of conception. Blood pressure declined during pregnancy while blood glucose rose. There were no morphologic changes in hair bulbs and only suggestive changes in liver cells that pointed to increased vacuolation. Increased metabolic efficiency during pregnancy enables the mother to safely pass through a long pregnancy during most of which she is fed a low-protein diet. Nonpregnant aminals suffer more under the same circumstances.

Albuminuria↗
PubMed1975

Protein deprivation in primates. V. Fetal mortality and neonatal status of infant monkeys born of deprived mothers.

Seventy-four pregnancies were followed in 45 rhesus monkeys. While pregnant the mothers were fed a semisynthetic diet affording 1, 2, or 4 g protein/kg per day. The poorer diets tended to produce excess fetal mortality, but liveborn infants born to 1-g and 2-g mothers averaged as large as those in the 4-g group. No differences existed in total protein concentration and albumin-globulin ratios in the sera of newborn infants.

Abortion, Spontaneous↗