Estrogen-induced alterations of hematoside of rat small intestinal mucosa

Prior studies have suggested that sex hormones could influence the ganglioside and/or neutral glycosphingolipid composition of various organs. To date, the effects of sex hormones on the glycosphingolipid composition of the rat small intestinal mucosa, however, have not been examined. In the present studies, male albino rats of the Sherman strain were subcutaneously administered the synthetic estrogen, ethinylestradiol (5 mg/kg body wt. per day), or diluent for 5 days, and the ganglioside, neutral glycosphingolipid and ceramide composition of the small intestinal mucosa of these animals were analyzed and compared. The results of these experiments demonstrate that estrogen administration: increased the ganglioside concentration of this tissue, including hematoside (Gm3); increased the percentage of the long-chain base phytosphingosine of hematoside; and did not appear to significantly influence the concentration or composition of the neutral glycosphingolipids or ceramide in this tissue. These data, therefore, indicate that estrogen administration induces quantitative and qualitative alterations in the gangliosides but not in the neutral glycosphingolipids or ceramide of rat small intestinal mucosa.     

Structural and compositional difference in the neutral glycolipids between epithelial and non-epithelial tissue of the mouse small intestine

Five major neutral glycolipids, GL-1-GL-5, were isolated from the the mouse small intestine. Their structures and distribution were determined by permethylation analysis, sequential degradation with exoglycosidases and/or immunohistochemistry. The molar ratio of GL-1, GL-2, GL-3, GL-4 and Gl-5 in the whole small intestine was 1:0.04:0.03:0.42:0.02. The structures of GL-1 and GL-4 present in epithelial cells were reported previously to be glucosyl ceramide and asialo G_M1, respectively (Umesaki, Y., Suzuki, A., Kasama, T., Tohyama, K., Mutai, M. and Yamakawa, T. (1981) J. Biochem. 90, 1731–1738). GL-5, also present in the epithelial cells, was fucosyl asialo G_M1, and fucose was shown to be linked to terminal galactose of asialo G_M1 in the manner of α(1–2) bond. GL-2 and GL-3, present in the residual tissue after scraping the mucosa, were determined to be globoside and Forssman glycolipid, respectively. Both globoside and Forssman glycolipid of the non-epithelial tissue had non-hydroxy fatty acid (C₁₆–C₂₄) in combination with sphingosine (C₁₈) as the ceramide components, in contrast with the ceramide structures of the epithelial glycolipids, which contained α-hydroxy fatty acids in combination with phytosphingosine. Immunohistochemical staining using anti-glycolipid antibodies confirmed the distribution of asialo G_M1 and fucosyl asialo G_M1, and Forssman glycolipid in the epithelial and non-epithelial tissue, respectively.     

THE DISTRIBUTION OF LIPIDS IN THE HUMAN NERVOUS SYSTEM-V. GANGLIOSIDES AND ALLIED NEUTRAL GLYCOLIPIDS OF INFANT BRAIN

—Gangliosides and allied neutral glycosylceramides were isolated from human infant (2-24 months of age) cerebral cortex and white matter. The individual glycolipids were separated quantitatively by a combination of column and thin-layer chromatographic methods on silica gel, DEAE-cellulose and Sephadex G-25. In cerebral cortex G_D1a and G_M1 were the major fractions and constituted more than 70 per cent of the total gangliosides. The concentrations of neutral glycolipids, except for galactosylceramides, were very low: lactosylceramide and glucosylceramide comprised 30 and 5 nmol/g wet weight, respectively. In white matter their concentrations were 10 times higher. The ganglioside concentration was only 50 per cent of that in cerebral cortex: the difference was accounted for mainly by the much lower content of the major di- and trisialogangliosides. Stearic acid was the predominant fatty acid of all brain gangliosides. G_M3, and G_D3 had a considerable content of the very long-chain fatty acids, C₂₂-C₂₄, particularly in the white matter. Glucosylceramide and lactosylceramide had almost identical fatty acid patterns between each other in cerebral cortex and white matter. In the cerebral cortex stearic acid and in the white matter the very long-chain acids predominated. d20:1 Sphingosine comprised more than 20 per cent of total sphingosine in all the gangliosides of the G_l- and G₂-series. G_M3, and G_D3 like lactosylceramide contained significantly less of d20:1 sphingosine. The findings suggest the existence of separate compartments for the biosynthesis of the gangliosides. Glucosylceramides and lactosylceramides of white matter have the same ceramide composition as the galactosylceramides with normal fatty acids and are thus unlikely to be intermediates in the metabolism of the major brain gangliosides which have a completely different fatty acid composition.     

Effects of Divalent Cations on the Glycolipids from Cultured Mouse Neuroblastoma Cells

Abstract: The influence of divalent cations on glycosphingolipid metabolism was examined in the NB41A mouse neuroblastoma clonal cell line. HPLC methods were utilized to quantitate the effects on neutral glycolipids and monosialogangliosides. NB41A cells were shown to contain G_M3, G_M2, G_M1, G_D3, and G_D1a by HPLC and TLC. The neutral glycosphingolipids consisted of glucosylceramide (GlcCer), lactosylceramide (LacCer), GaINAc(β1→4) Gal(β1→4)Glc(β1→1)Cer (GgOse₃Cer), and GaINAc(β1→3)Gal(α1→4) Gal-(β1→4)Glc(β1→1)Cer (GbOse₃Cer) according to their HPLC behavior. Cells grown in the presence of 1.85 mm -EGTA showed a two- to threefold increase in G_M3 whereas other glycosphingolipids were only slightly affected. When cells were grown in the presence of 1.45 mm -EGTA plus 0.4 mm -EDTA a similar increase in G_M3 was observed but this change was now accompanied by decreases in G_M2, G_M1 GgOse₃Cer, and GbOse₄Cer. The EGTA-EDTA effects were reversed when growth was in the presence of Ca²⁺ sufficient to bind all chelator. Mn²⁺ replacement reversed the chelator effects differentially; G_M2 and G_M1 levels were the most sensitive to increases in Mn²⁺ concentration; GgOse₃Cer and GbOse₄Cer were also sensitive, whereas G_M3 was the least affected. These results suggest calcium serves an important regulatory role on G_M3 levels and that manganese concentration may regulate the levels of galactosamine-containing glycolipids in mouse NB41A neuroblastoma cells.     

The glycosphingolipid composition and glycosyltransferase activities of the small intestinal mucosa of testosterone-treated rats

Prior studies have demonstrated that sex hormones can influence the glycosphingolipid composition of different organs, including small intestine. However, to date, the effects of testosterone on glycosphingolipids of rat small intestinal mucosa have not been examined. Experiments were conducted to examine the effect of subcutaneous administration of synthetic testosterone (500 micrograms/100 g body wt.) on the gangliosides and neutral glycosphingolipids of rat small intestinal mucosa. Their results demonstrated that testosterone administrations: (i) increased the ganglioside content including hematoside (GM3); (ii) increased the total content of neutral glycosphingolipids, which was due to the increases in glucosylceramide and globotriaosylceramide; (iii) increased the activities of cytidine 5'-monophosphate-N-acetylneuraminic acid: lactosylceramide sialyltransferase, and UDPgalactose: lactosylceramide galactosyltransferase; (iv) increased the percentage of the long chain base phytosphingosine in hematoside, glucosyl-, and globotriaosylceramide; and (v) significantly altered the fatty acid composition of each of these glycosphingolipids. These results demonstrate that administration of testosterone induces alterations in glycosphingolipid composition and glycosyltransferases activities in rat small intestinal mucosa.     

GLYCOSPHINGOLIPIDS IN FETAL TAY-SACHS DISEASE BRAIN AND LUNG CULTURES

Abstract— A study was undertaken of the glycosphingolipids in cell cultures derived from cerebellum of Tay-Sachs disease fetal brain in order to determine the suitability of such cell strains as a model for Tay-Sachs disease. The glycosphingolipids in the Tay-Sachs disease cultured cerebellar cells were compared with those found in normal cultured cerebellar cells, normal and Tay-Sachs cultured lung cells, and normal and Tay-Sachs fetal brain. The glycolipids were separated by TLC, then analyzed by GLC of the trimethylsilyi derivatives of the methylglycosides of the sugar moieties. In the cultured cerebellar lines, the predominant gangliosides were G_M2, G_M3, and G_D3. There was a 4-fold increase of G_M2 in the Tay-Sachs as compared with the normal line. Only G_M3 and G_D3 gangliosides were found in the Tay-Sachs and the normal fetal lung cell cultures. The major neutral glycosphingolipids in all of the cultured cells which were analyzed were glucosylceramide, lactosylceramide, digalactosyl-glucosylceramide, and globoside. When the Tay-Sachs cerebellar cells were labelled with [1-¹⁴C]gluco-samine, some radioactivity was observed in the trihexosylceramide band, indicating the presence of a small amount of a galactosamine-containing trihexosylceramide which may be asialo-G_M2 (G_A2). The trihexosylceramide in Tay-Sachs fetal brain was identified as G_A2 by GLC. Both Tay-Sachs and normal fetal brain gangliosides were more complex than those found in the cultured cells. Long chain fatty acids (C_24:0 and C_24;1) predominated in all of the glycosphingolipids of the Tay-Sachs and the normal cultured cerebellar cells. In contrast, the glycosphingolipids of Tay-Sachs and normal fetal brain contained mainly the shorter chain fatty acids (C₁₆:₀, C₁₈:₀, and C_18:1). The cerebrosides in both the Tay-Sachs and normal fetal brains were mainly glucosylceramide with only small amounts of the galactosylceramide which predominates in infant brain. Cultured cells from the fetal Tay-Sachs disease     

Binding of soybean agglutinin to glycolipid components of porcine lymphocyte plasma membranes

¹²⁵I-Labeled soybean agglutinin binds primarily to glycolipids contained in pig lymphocyte plasma membranes as measured by in situ “staining” of membranes subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Separation of these glycolipids by differential extraction, silicic acid chromatography, and high-performance thin-layer chromatography showed that three different species of plasma membrane glycolipid bind this lectin; trihexosyl ceramide, globoside, and ganglioside G_M2 in order of increasing affinity (over a range of 10- to 20-fold). Trihexosyl ceramide and globoside, major neutral membrane glycolipids, are the major binders; while G_M2, a minor acidic glycolipid, is a quantitatively smaller lectin-binding component.     

Thermotropic behavior of binary mixtures of diplamitoylphosphatidylcholine and glycosphingolipids in aqueous dispersions

The thermotropic behavior of mixtures of dipalmitoylphosphatidylcholine (DPPC) with natural glycosphingolipids (galactosylceramide, phrenosine, kerasine, glucosylceramide, lactosylceramide, asialo-G_M1, sulfatide, G_M3, G_M1, G_D1a, G_T1b) in dilute aqueous dispersions were studied by high sensitivity differential scanning calorimetry over the entire composition range. The pretransition of DPPC is abolished and the cooperativity of the main transition decreases sharply at mole fractions of glycosphingolipids below 0.2. All systems exhibit non-ideal temperature-composition phase diagrams. The mono- and di-hexosylceramides are easily miscible with DPPC when the proportion of glycosphingolipids in the system is high. A limited quantity (1–6 molecules of DPPC per molecule of glycosphingolipid (GSL) can be incorporated into a homogeneously mixed lipid phase. Domains of DPPC, immiscible with the rest of a mixed GSL-DPPC phase that shows no cooperative phase transition, are established as DPPC exceeds a certain proportion in the system. One negative charge (sulfatide) or four neutral carbohydrate residues (asialo-G_M1) in the oligosaccharide chain of the glycosphingolipids results in phase diagrams exhibiting coexistence of gel and liquid phases over a broad temperature-composition range. Systems containing gangliosides show complex phase diagrams, with more than one phase transition. However, no evidence for phase-separated domains of pure ganglioside species is found. The thermotropic behavior of systems containing DPPC and glycosphingolipids correlates well with their interactions in mixed monolayers at the air/water interface.     

Incorporation and degradation of GM1 ganglioside and asialoGm1 ganglioside in cultured fibroblasts from normal individuals and patients with β-galactosidase deficiency

The uptake and degradation of G_M1 ganglioside (G_M1) and asialoG_M1 ganglioside (G_A1) were studied in cultured fibroblasts from normal individuals and patients with β-galactosidase deficiency, using the lipid-loading test. The glycolipids were incorporated from the media into the fibroblasts and the terminal galactose was hydrolyzed in normal cells. The hydrolysis rates of G_A1 were 80–86% of normal on the 3rd day after loading, while G_M1 was hydrolyzed slowly; 35–54% on the 14th day. In infantile G_M1 gangliosidosis and I-cell disease, little G_M1 and G_A1 was hydrolyzed on any day of culture, while fibroblasts from patients with adult G_M1 gangliosidosis, Morquio disease type B and galactosialidosis hydrolyzed the lipids at nearly normal rates. The intracellular accumulation of the glycolipids, on the basis of protein content, was abnormally high in the case of infantile G_M1 gangliosidosis and I-cell disease, but normal in the other disorders examined. These observations indicate that the in situ metabolism of G_M1 and G_A1 is probably normal in fibroblasts from patients with adult G_M1 gangliosidosis, Morquio disease type B and galactosialidosis, although in vitro β-galactosidase activities in these disorders are very low. The results are compatible with findings that G_M1 and G_A1 do not accumulate in the somatic organs of patients with adult G_M1 gangliosidosis and galactosialidosis. In I-cell disease, however, the results of the loading test did not agree with the finding that there is little accumulation of glycolipids in postmortem tissues.     

Neutral glycolipids of atherosclerotic plaques and unaffected human aorta tissue

The composition, structure and localization of neutral glycosphingolipids of human aorta taken from subjects who had died after myocardial infarction were studied. Individual glycosphingolipids were purified by high-performance liquid chromatography and were characterized on the basis of their chromatographic mobility, carbohydrate composition, methylation analysis and by 1H-NMR spectroscopy. The main aortic glycosphingolipids were identified as glucosylceramide, lactosylceramide, globotriaosylceramide and globotetraosylceramide. Significant differences in the neutral glycosphingolipid composition of intima and media were detected. The neutral glycosphingolipid profile of medial plaques resembled that of unaffected media; however, significant differences were detected between intimal plaques and unaffected intima. Whereas the latter contained trihexosylceramide and globoside as the only neutral glycolipids, the intimal plaque glycolipids consisted mainly of glucosylceramide and also contained appreciable amounts of lactosylceramide which were completely absent in the unaffected intima. In comparison to intimal plaques, unaffected intima is characterized by a much higher content of cerebrosides terminating by beta-galactosyl residues which are known to interact with growth factors and other external stimuli. It thus seems possible that the proliferative activity of smooth muscle cells in atherosclerotic diseases is to some extent associated with their neutral glycolipid profile.     

Glycosphingolipids of human urothelial cell lines with different grades of transformation

Neutral glycolipids and gangliosides from seven human urothelial cell lines, differing in grades of transformation (TGr), were characterized by fast atom bombardment mass spectrometry, exoglycosidase treatment and an immunostaining procedure. The major neutral glycolipids identified in all cell lines studied included CMH, CDH, CTH, globoside and paragloboside, the gangliosides were G_M3, G_M2, sialosylparagloboside and G_D1a. The following observations were made: 1. G_M2 was the major ganglioside in the TGrll cell lines (non-tumorigenic, non-invasive), but a minor component in the TGrIII cell lines (tumorigenic, invasive). 2. All components showed C16:0 and C24:0 as major fatty acids, but in the TGrIII cell lines the fatty acid composition of CMH and some of the gangliosides were more complex showing unsaturated and hydroxy-fatty, acids as well.Abbreviations CMH Monohexosylceramide - CDH Lactosylceramide (Galß1-4GlcCer) - CTH Globotriaosylceramide (Gal1-4Galß1-4GlcCer) - Globoside (GalNAcß1-3Gal1-4Galß1-4GlcCer) - Paragloboside (Galß1-4GlcNacß1-3Galß1-4GlcCer) - 3L_M1 Slalosylparagloboside (Neu5Ac2-3Galß1-4GlcNacß1-3Galß1-4GlcCer) - Aslalo-G_M2 (GalNAcß1-4Galß1-4GlcCer) - AsialoG_M1 (Galß1-3GalNAcß1-4Galß1-4GlcCer) - Hex Hexosyl - HexNAc 2-acetamido-2-deoxyhexosyl - HPTLC high performance thin layer chromatography - FAB-MS fastatom bombardment mass spectrometry - TGr transformation grade Ganglios are named according to Svennerholm [1]     

Effects of ganglioside GM1 on DNA synthesis in isolated nuclei and on the activity of DNA polymerase α derived from S-phase HeLa cells

Ganglioside G_M1 inhibited either DNA synthesis in isolated nuclei or the activity of DNA polymerase α fractionated from S-phase HeLa cells. The concentrations of G_M1 necessary for 50% inhibition were about 5 μM and 10 μM for nuclei and DNA polymerase α, respectively. The G_M1 inhibition of the enzyme activity was suppressed by the addition of 0.05% Triton X-100. Neither gangliotetraosylceramide (asialo-G_M1) nor free N-acetylneuraminic acid inhibited the enzyme activity. These facts suggest that G_M1, probably in the form of micelles, could influence the enzyme activity by behaving as a polyanionic macromolecule. The kinetic studies indicate that the G_M1 inhibition of the enzyme activity was not competitive with the substrate, deoxythymidine triphosphate, but rather with the template DNA. Binding of G_M1 and DNA polymerase α was suggested by the cocentrifugation of G_M1 and the enzyme fraction after their preincubation. It was also observed that other acidic glycolipids, i.e., brain sulphatide and seminolipid, also inhibited the enzyme activity, whilst neutral galactosylceramide did not. The inhibitory influences of these sulphate esters of glycolipids were, similarly to G_M1, suppressed by the addition of 0.05% Triton X-100.     

High-performance thin-layer chromatography and densitometric determination of brain ganglioside compositions of several species.

Improved resolution of complex brain ganglioside mixtures was achieved by high-performance thin-layer chromatography. The percentage distribution of individual gangliosides was then determined by direct densitometric seanning, employing a transmittance mode, of the resorcinol-positive spots on the plate. As little as 90 pmol (29 ng) of lipid-bound sialic acid could be detected with a good signal-to-noise ratio. A linear detector response was observed up to 3.0 μg of lipid-bound sialic acid. The brain white matter ganglioside patterns of eight animal species, including human, chimpanzee, monkey, chicken, bovine, sheep, and pig, were examined in detail. In addition, human brain gray matter, rat cerebral, rat brain gray matter, and rat cerebellar ganglioside patterns were also studied. Ganglioside G_M4 (G₇) was found to be one of the major components in primate and chicken brain white matter, but it represented only a minor ganglioside in other species. Other major gangliosides in all brain samples studied were G_M1, G_D1a, G_D1b, and G_T1b. G_M1 was more abundant in white matter than in gray matter. G_T1a, a recently discovered ganglioside species, was found in all species examined, but was most abundant in the rat cerebellum. The latter source also contained high proportions of G_T1b and G_Q1b.     

Tissue distribution of EDTA encapsulated within liposomes containing glycolipids or brain phospholipids

Multilamellar liposomes were prepared with various asialoglycolipids, gangliosides, sialic acid, or brain phospholipids in the liposome membrane and with ethylenediaminetetraacetic acid (EDTA) encapsulated in the aqueous compartments. The liposomes containing glycolipids or sialic acid were prepared from a mixture of phosphatidylcholine, cholesterol, and one of the following test substances: galactocerebroside, glucocerebroside, galactocerebroside sulfate, mixed gangliosides, monosialoganglioside G_M1, monosialoganglioside G_M2, monosialoganglioside G_M3, disialoganglioside G_D1a, or sialic acid. The liposomes containing brain phospholipids were mixtures of either sphingomyelin and cholesterol or a brain total phospholipid extract and cholesterol. Distribution of ¹⁴C-labeled EDTA were determined in mouse tissues from 15 min to 6 h or 12 h after a single injection of liposome prepartion. Liver uptake of encapsulated EDTA was lowest from all liposome preparations containing sialic acid or sialogangliosides regardless of the amount of sialic acid moiety present or the identity of the particular ganglioside; highest uptake of encapsulated EDTA by liver was from the liposomes containing galactocerebroside or brain phospholipids. Lungs and brain took up the largest amounts of EDTA from liposomes containing sphingomyelin and lesser amounts from liposomes containing G_D1a. Use of mouse brain phospholipid extract to prepare liposomes did not increase uptake of encapsulated EDTA by the brain. EDTA in liposomes containing monosialogangliosides, brain phospholipids, galactocerebroside, or sialic acid was taken up well by spleen and marrow. Highest thymus uptake of encapsulated EDTA was from liposomes containing G_D1a. These results demonstrate that inclusion of sialogangliosides in liposome membranes decreases uptake of liposomes by liver, thus making direction of encapsulated drugs to other organs more feasible. Liposomes containing glycolipids also have potential uses as probes of cell surface receptors.     

Gangliosides and neutral glycosphingolipids of normal tissue and oat cell carcinoma of human lung

Concentration and composition of gangliosides and neutral glycosphingolipids of adult human lung, and lung small cell carcinoma were studied. The structures of the glycolipids were determined by quantitative component determination, enzymic degradation, permethylation and fast atom bombardment mass spectrometry. Adult human lung contained mainly gangliosides with lactosylceramide as the basic core, GM3, GD3 and GT3, and approx. equal proportions (10%) of gangliosides of the gangliotetraosyl- and lactotetraosylceramide series. 18 gangliosides with different carbohydrate moieties were identified: four of them were only found in the tumor tissue. The adult human lung contained 85 nmol (77-120) gangliosides and 140 nmol neutral glycosphingolipids per g wet weight. Globoside was the major neutral glycolipid and there were only minor amounts of glycolipids of the lactotetraose series. In small cell carcinoma tissue the concentration of neutral glycosphingolipids was approximately twice as high than in normal lung tissue, and there was a markedly larger concentration of both lactosylceramide and glycolipids of the lactotetraose series and fucose derivatives of these. The concentration of gangliosides varied between 202 and 415 nmol per g wet weight. Compared to normal lung tissue, the tumor tissue had a lower proportion of GD3, and a higher proportion of complex gangliosides, and they contained five tumor-associated gangliosides: Fuc-GM1, Fuc-GD1b, 3'-LM1, Fuc-3'-LM1 and 6'-nLM1.     

Glycolipid-dependent interaction between human migration-inhibitory factor and mononuclear phagocytes

It has been previously established in the guinea pig that the response of peritoneal macrophages to migration inhibitory factor (MIF) is enhanced by a macrophage glycolipid and that gangliosides reversibly bind MIF. This suggests that glycolipids function as cell surface receptors for MIF. In this report, it is demonstrated that the response of human peripheral blood monocytes to human MIF is augmented by preincubation of these cells with glycolipidenriched material extracted from the human macrophage-like cell line U937 or human peripheral blood monocytes and with a purified glycolipid from guinea pig peritoneal macrophages. In addition, a mixed ganglioside preparation from bovine brain shows the same effect. In contrast, the pure gangliosides, G_M1 and G_D1a, and glycolipids from the HL-60 cell line, which is a MIF-unresponsive cell line, were not able to enhance the response to human MIF. The specificity of enhancement by particular glycolipids could not be attributed to an increased uptake of only enhancing glycolipids since there was no significant difference between the association of monocytes with radioactive liposomes containing biologically active or inactive glycolipids. Pronase treatment did not affect the enhancing activity of the U937 glycolipidenriched material. Incubation of cells with glycolipids results in enhancement only if done at 37 °C and not at 4 °C. Therefore, the association of lipid with the monocyte surface appears to be dependent on temperature.Further evidence for the receptor nature of these enhancing glycolipids is provided by experiments involving affinity purification experiments. Coupling of bovine brain mixed gangliosides to agarose resulted in a matrix capable of reversibly binding MIF. G_D1a-agarose was inactive in this respect.     

Comparison of the 13C-n.m.r. spectra of gangliosides GM1 with those of GM1-oligosaccharide and asialo-GM1

The ¹³C-n.m.r. spectra of asialo-G_M1 and G_M1-oligosaccharide are completely assigned and compared to those previously found for intact G_M1 and for the series G_M4, G_M3, G_M2, G_M1, G_D1a, G_D1b, and G_T1b. Removal of the ceramide residue from G_M1 liberated a free, reducing aldehyde group, which was reflected in a doubling of the ¹³C-n.m.r. signals assignable to the d-glucose residue because of α,β equilibrium. The spectrum of asialo-G_M1 lacks the resonances from the sialic acid residue, as expected; in addition, several resonances from the neutral gangliotetraglycosyl residue shifted to different field positions after removal of sialic acid from G_M1. These resonances include that of C-4 of the inner β-d-galactosyl residue, and C-1 of the 2-acetamido-2-deoxy-d-galactosyl residue that is near the site of attachment of the sialosyl residue. The differences between the chemical shifts of the carbon resonances of oligomeric and monomeric saccharides, termed linkage shifts, provide a quantitative assignment aid. They are ～ $\text{1}\text{3}$ of those for residues linked to sialic acid than those for residues linked to the neutral hexose chain. Correlations among linkage shifts for pairs of glycosidically-linked carbon atoms for asialo-G_M1 and G_M1-oligosaccharide were compared with those for the series of gangliosides G_M4 to G_T1b, and differences are noted for resonances for carbon atoms near the sialic acid residue. The spectrum of ganglioside G_M1b, a positional isomer of G_M1 whose ¹³C-n.m.r. spectrum has not yet been observed, is predicted.     

Monosialoganglioside liposome-entrapped enzyme uptake by hepatic cells

Monosialogangliosde liposomes are rapidly taken up by the liver as compared to dicetylphosphate, phosphatidic acid or neutral liposomes. Asialoganglioside G_{M 1} liposomes are taken up with the same avidity as ganglioside G_{M 1} liposomes. Competition experiments with asialofetuin suggest that this uptake is mediated by specific recognition of the terminal galactose residues of the glycolipid liposomes by the receptor present on the plasma membrane of the parenchymal cells of liver. Thus liposomes containing glycolipids with terminal β-galactosyl residues should provide an approach for specifically directing biologically active molecules to liver parenchymal cells.     

Some patterns in dimer II formation in BODIPY-FL-labeled lipids

Some patterns of dimer II formation from BODIPY-FL-labeled lipid probes using mono-, bis-, and tris-BODIPY-FL derivatives of gangliosides G_M1 and G_D1a and mono- and bis-BODIPY-FL derivatives of triglycerides have been defined. BODIPY-FL-labeled glycolipids were shown in phospholipid layers to reveal a greater disposition towards dimer II formation than BODIPY-FL-labeled glycerides. The formation of dimer II was also shown to depend on the label position in the probe molecule. Probes bearing a label in the polar head area are more prone to dimer II formation than probes labeled in the apolar part of the molecule.     

Oncofetal expression of Lex carbohydrate antigens in human colonic adenocarcinomas. Regulation through type 2 core chain synthesis rather than fucosylation

The mechanism of expression of a series of glycolipid antigens carrying the Lex determinant structure, Gal beta 1----4[Fuc alpha 1----3]GlcNAc beta 1----, and characterized by oncofetal expression in fetal colon and colonic adenocarcinomas has been studied in human fetal and adult proximal colon tissue. Results presented from TLC immunostain analysis of neutral glycolipids isolated from normal adult colonic mucosa have indicated the presence of only barely detectable quantities of both an Lex-active glycolipid that co-migrated with III3V3Fuc2nLc6 and its precursor nLc6. These structures were found in large quantities in glycolipid fractions from human adenocarcinoma tumors and human small cell lung carcinoma NCI-H69 cells. In contrast, type 1 chain-based Lea antigen structures were found in both normal mucosa and adenocarcinomas. Analysis of gangliosides of normal colonic mucosa by TLC immunostain indicated the presence of a series of type 2 chain-based gangliosides; however, sialyl-Lex was not detected. The ability of normal colonic mucosa to synthesize type 2 chain core structures was demonstrated by the presence of a beta 1----4 galactosyltransferase activity with Lc3 as an acceptor in an amount equivalent to 60-65% of the total galactosyltransferase activity. An alpha 1----3 fucosyltransferase was also found to be expressed in significant quantity in adult colonic mucosa. Kinetic studies indicated that this is most probably the alpha 1----3/4 fucosyltransferase suggested to be a product of the Lewis gene (Le). Thus, although normal adult colonic mucosa contained the enzymes to synthesize Lex and sialyl-Lex structures, these antigens were not found. Tissue immunofluorescence studies indicated that type 2 chain precursors and the alpha 1----3/4 fucosyltransferase were found in different cell populations in adult proximal colonic mucosa. However, both type 2 chain core structures and their fucosylated derivatives were found to be associated with epithelial cells of fetal colon. These results indicate that oncofetal expression of Lex antigens in fetal colonic epithelium and in adenocarcinomas but not in normal adult mucosa is due to the retrogenetic expression of type 2 chain precursors which are not found in normal adult colonic epithelial cells.