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PubMed1989

[Metabolic cooperation in cocultures of fibroblasts from patients with various abnormalities of galactose metabolism].

14C galactose incorporation into the TCA-precipitable material of cultures of fibroblasts deficient in galactokinase (GALK-) was nil. In cultures of fibroblasts deficient in uridyltransferase (GALT-), it was 30 to 75% of control incorporation. In cocultures of GALK and GALT-deficient fibroblasts, 14C incorporation was restored to near-normal levels. This restoration produced in the presence of close cellular contacts was not increased by polyethyleneglycol somatic hybridization. Our results indicate that metabolic cooperation occurred involving the transfer of galactose 1-phosphate from the GALT-deficient to the GALK-deficient cells via intercellular connections.

Carbohydrate Metabolism, Inborn Errors↗
PubMed1989

Structure of phosphonoglycosphingolipid containing pyruvylated galactose in nerve fibers of Aplysia kurodai.

A phosphonoglycosphingolipid, designated as FGL-IIb, was identified in nerve fibers of Aplysia kurodai by two-dimensional thin layer chromatography (Abe, S., Araki, S., and Satake, M. (1986) Biomed. Res. (Tokyo) 7, 47-51). FGL-IIb was isolated from the nervous system of A. kurodai by Iatrobeads column chromatography using three solvent systems. Pyruvic acid was identified by thin layer chromatography as its 2,4-dinitrophenylhydrazone and established by permethylation studies to be attached as a ketal to O-3 and O-4 of the terminal galactose of the oligosaccharide chain in FGL-IIb. By sugar analysis, permethylation studies, fast atom bombardment-mass spectrometry, and proton magnetic resonance spectrometry, the structure of FGL-IIb was concluded to be [3,4-O-(1-carboxyethylidene)]Gal beta 1----3GalNAc alpha 1----3(Fuc alpha 1----2) (2-aminoethylphosphonyl----6)Gal beta 1----4Glc beta 1----1ceramide. Its major aliphatic components were palmitic acid, octadeca-4-sphingenine and anteisononadeca-4-sphingenine. This is the first report of the occurrence of pyruvylated galactose as a constituent of animal sphingolipid.

Acidic Glycosphingolipids↗
PubMed1988

The active site of galactose oxidase.

The copper enzyme galactose oxidase has been prepared in three distinct redox modifications; two of these represent nearly homogeneous preparations of active and inactive species which have been described previously, while the third has never before been reported. Preparation of these redox modifications as homogeneous species has permitted detailed spectroscopic and catalytic studies of each for the first time. We find that the form which has been extensively probed by EPR spectroscopy is devoid of catalytic activity and does not interact with substrate. The detailed characterization of oxidatively activated galactose oxidase and its anion interactions has led to a spectroscopic assignment of the copper oxidation state in this complex which indicates that the one-electron redox process which converts the inactive form to catalytically active enzyme is associated with oxidation of the protein rather than the metal center as has been proposed previously. This oxidation step is required for catalytic activity and is the basis of the two-electron redox reactivity for the enzyme active site: anaerobic addition of hydroxylic substrates results in reduction of the two-electron redox unit, and the spectral features associated with both the copper ion and the non-metal redox center are eliminated, apparently forming a cuprous site. The two-electron reactivity resulting from protein participation in redox catalysis has important implications in this and other mechanisms where oxygen reduction occurs at a mononuclear metal ion active site.

Binding Sites↗
PubMed1988

Solvent exchangeable protons and the activation of molecular oxygen: the galactose oxidase reaction.

The reduction of O2 to H2O2 requires two protons as well as two electrons. Thus, activation of dioxygen reasonably may involve either general or specific acid catalysis. Consequently, the reduction of O2 to H2O2 could exhibit a kinetic solvent isotope effect (KSIE). The reaction catalyzed by the mononuclear Cu(II) enzyme, galactose oxidase does exhibit a KSIE (+1.55). The pL-rate profile exhibits an alkaline shift in D2O which can be attributed to the differential partitioning of H+ versus D+ between bulk water and a metal-bound H2O (delta pKa = +0.19). A variety of spectral evidence places an equatorial, Cu(II)-liganded water molecule at the active site of galactose oxidase. The analysis of the KSIE data is detailed and the potential generality of the function of such metal-bound H2O at other type 2 Cu(II) sites is discussed.

Galactose Oxidase↗
PubMed1986

[The influence of carrageenan, colchicine, 2,4-dinitrophenol, ethanol, galactose, indomethacin and liquoid on hemolytic complement activity (CH50E)].

The influence of Liquoid (0.00005, 0.00001%), Carrageenan (0.001% up to 0.000001%), Colchicine (0.01% up to 0.0025%), Indomethacin (1 X 10(-4) up to 2.5 X 10(-5) mol/1), Ethanol (10% up to 1.25%), Galactose (1 X 10(-1) up to 1 X 10(-2) mol/l) and 2.4-Dinitrophenol (5 X 10(-4) up to 1 X 10(-5) mol/l) on the total hemolytic activity of complement was tested. By Liquoid, Carrageenan, Colchicine and Ethanol in all studied concentrations an remarkable inhibition of the CH50E could be estimated. Indomethacin up to an concentration of 3.75 X 10(-5) mol/l reduced the activity partially. In contrast, Galactose and 2.4-Dinitrophenol have not influenced the complement titers.

2,4-Dinitrophenol↗
PubMed1987

Quantification and localization of galactose-specific binding sites in rat liver during postnatal development.

We investigated the number and distribution of galactose-specific binding sites in developing livers from suckling rats of various ages using Lac-BSA-Au5 (lactosylated bovine serum albumin adsorbed onto colloidal gold particles 5 nm in diameter) as electron-dense ligand, and performing transmission electron microscopy of the specimen. It has been reported that the number of galactose-specific binding sites increases rapidly during organ development post partum (p.p.) and this was ascribed to hepatocyte receptor increase only. We now have investigated in in situ and in vitro experiments whether the binding sites of identical sugar specificity but located on sinusoidal cells show the same increase in expression or are independently regulated. We therefore quantified the number of particles bound by isolated hepatocytes and liver macrophages and found a gradual increase of both binding activities with age, the binding levels of adult liver cells being reached at day 15 p.p. This was confirmed with experiments using in situ prefixed organs thus proving the validity of this finding also for the intact organ. In both sets of experiments--in vitro as well as in vivo--ligand was found binding statistically distributed as single particles on hepatocytes of all ages, whereas on liver macrophages the binding pattern changed during development. On liver macrophages from rats 15 days of age ligand binding occurs in the preclustered pattern described for macrophages from adult rat livers whereas liver macrophages of newborn rats express a different binding pattern: they bind the ligands mostly as single particles with only few and small microaggregates.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1977

Effect of corticosteroids on the response of lymphocytes to stimulation by galactose oxidase-modified lymphocytes.

Human peripheral blood mononuclear cell preparations, after treatment by neuraminidase plus galactose oxidase, stimulated untreated lymphocytes. The increases in tritiated thymidine incorporation in the responder lymphocytes were observed after 48 h of mixed cell cultures. Monocytedepleted lymphocyte preparations were equally effective stimulator cells. Both purified T and B fractions were effective stimulator cells. On the other hand, only the T but not the B fractions could respond to the stimulation. The response of the cells to this type of stimulation was suppressed by 10(4)-10(7) M of the corticosteroid preparation methylprednisolone. When the cells treated with neuraminidase plus galactose oxidase were cultured alone for 48 h, they lost their stimulating capacity. However this loss could not be prevented by the presence in the culture of methylprednisolone. Hence the drug has selective suppressive activity on one type of lymphocyte activity but not the other.

Adrenal Cortex Hormones↗
PubMed1986

Effects of aldose reductase inhibitor, CT-112, on sugar alcohol accumulation in corneal epithelium of galactose-fed rats.

A study was made of inhibitory effects of an aldose reductase inhibitor, CT-112 (5-(3-ethoxy-4-pentyloxyphenyl)-2,4-thiazolidinedione) ophthalmic solution, on the accumulation of sugar alcohol (dulcitol) in the corneal epithelium of rats fed on a 50% galactose diet. The effects were correlated with the concentrations of the drug solution. The rats were divided into 6 groups. One group was fed on a regular laboratory chow and was untreated. The other 5 groups were fed on a 50% galactose diet, and 0.1, 0.25, 0.5 or 1.0% CT-112 ophthalmic solution or its vehicle was instilled in both eyes 4 times a day in each of the 5 treated groups. After 2 weeks, the corneal epithelium was scraped off in all rats and its dulcitol content was determined by gas chromatography. CT-112 ophthalmic solution was found to inhibit the accumulation of dulcitol in a dose-dependent manner, except for the 1.0% solution which had an activity comparable to the 0.25% solution.

Aldehyde Reductase↗
PubMed1975

Ethanol and galactose metabolism as influenced by 4-methylpyrazole in alcoholics with and without nutritional deficiencies. Preliminary report of a new approach to pathogenesis and treatment in alcoholic liver disease.

4-Methyl pyrazole (4-MP, a specific inhibitor of alcohol dehydrogenase) reduced ethanol elimination by 30-50% and completely removed the ethanol-induced inhibition of galactose elimination in 2 control subjects. Ethanol elimination was accelerated in 2 alcoholics with adequate nutrition, but the effect of 4-MP was comparable to that in controls. In 2 other alcoholic subjects, who reported poor nutritional intake, intermediate rates of ethanol elimination were observed and 4-MP had almost no effect on ethanol or galactose elimination. These results suggest that alcohol abuse may result in an increased contribution to ethanol elimination by pathways other than that involving alcohol dehydrogenase (ADH) and that the decreased contribution from ADH, possibly potentiated by inadequate nutrition, may diminish the ethanol-induced shift in the NAD-coupled redox state. Since liver damage produced by alcohol abuse is believed to be related to changes from the normal redox state caused by ethanol, these results may explain why alcoholic liver damage is uncommon in alcoholics living on a marginal diet. Since 4-MP effectively eliminates the ethanol-induced shift in the redox state, a therapeutic trial with 4-MP in alcoholics with a high risk for liver disease is indicated.

Adult↗
PubMed1988

Occurrence of sulfate in the asparagine-linked complex carbohydrate units of thyroglobulin. Identification and localization of galactose 3-sulfate and N-acetylglucosamine 6-sulfate residues in the human and calf proteins.

Human thyroglobulin glycopeptides representing the multiple asparagine-linked complex (unit B) carbohydrate units of this protein were found to contain substantial amounts of sulfate (ranging from 0.5 to 2.5 mol/mol of oligosaccharide); this substituent was shown to occur primarily in the form of terminal beta-linked Gal-3-SO4 residues which represent novel capping groups occurring alternatively to sialic acid and in comparable amounts. Upon hydrazine/nitrous acid fragmentation and radiolabeling with NaB3H4, all human unit B DEAE-resolved glycopeptide fractions yielded an acidic disaccharide which was characterized as Gal-3-SO4 beta 1----4-anhydromannitol. Studies on glycopeptides modified by desialylation, desulfation, and beta-galactosidase treatment indicated that the majority (approximately 70%) of the complex carbohydrate units contain sulfate groups and that Gal-3-SO4 and sialic acid residues can coexist in terminal positions on the same N-linked oligosaccharide. In addition to Gal-3-SO4, the most acidic unit B variants were found to contain GlcNAc-6-SO4 which was recovered as Gal beta 1----4-anhydromannitol-6-SO4 after hydrazine/nitrous acid treatment and NaB3H4 reduction. On the basis of chromatography on immobilized concanavalin A, it was determined that whereas the Gal-3-SO4 groups occur on biantennary as well as more highly branched carbohydrate units, GlcNAc-6-SO4 is exclusively present in the latter oligosaccharides. In contrast to the N-linked carbohydrate units, the previously described O-linked glycosaminoglycan chain of human thyroglobulin yielded GlcA beta 1----3-anhydrotalitol-6-SO4 upon hydrazine/nitrous acid/NaB3H4 treatment, indicating that it is a chrondroitin 6-sulfate-like polymer. The distribution of sulfate in the complex oligosaccharides of calf thyroglobulin was quite different from that in the human protein; sulfate was not detectable in most of the glycopeptides and was sequestered in a single multibranched complex-type glycopeptide fraction (1.6 mol of sulfate/mol of oligosaccharide) which contained about equal amounts of Gal-3-SO4 and GlcNAc-6-SO4. The difference in galactose sulfation between human and calf thyroglobulins may be related to the substitution in the latter protein of some of the galactose residues by alpha-D-Gal capping groups.

Acetylglucosamine↗
PubMed1988

Influence of VIP on D-galactose transport across rabbit jejunum in vivo.

D-galactose absorption during 1 min perfusion periods was not affected by the presence of 10(-7)-10(-8) M VIP in the sugar solution, but exposure of mucosa to VIP for 5 min inhibited sugar absorption in the subsequent periods of perfusion. This inhibition is reversed after washing with saline solution. The effect of VIP disappeared when 10(-6) M RMI 12330A was added to the incubation solution together with 10(-7) M VIP and 1 mM D-galactose solution. These results suggest the existence of VIP receptors on the brush border membrane. The action of VIP could be mediated through the cAMP system.

Animals↗
PubMedDate not supplied

[A study of membrane glycoproteins from the rat brain using D-galactose-specific lectin].

Immobilized D-galactose-specific lectin from Zea mais was used to purify rat brain membrane glycoproteins. The membrane glycoproteins preliminarily washed from soluble proteins were solubilized consecutively by 2% triton X-100 and 1% SDS. PAG-electrophoresis with SDS and 2-mercaptoethanol revealed 10 polypeptide bands (Mm 109, 62, 59, 54, 51, 42, 16, 14, 12.5 and 12 kDa) in the membrane fraction of glycoproteins solubilized with triton X-100. Additional solubilization with SDS revealed 3 bands (Mm 109, 62, and 54 kDa). Only 3 polypeptide bands (Mm 62, 59, 42 kDa) were identified when analogous procedure was used for purification of the rat liver glycoproteins. Horse radish peroxidase labelled D-galactose-specific lectin from Zea mais was found to bind to neuron bodies and neurites in the cerebellum. It is suggested that the identified brain-specific membrane glycoproteins may take part in the cell adhesion between neurons.

Animals↗
PubMed1988

The immobilized leukoagglutinin from the seeds of Maackia amurensis binds with high affinity to complex-type Asn-linked oligosaccharides containing terminal sialic acid-linked alpha-2,3 to penultimate galactose residues.

We recently reported that the purified leukoagglutinin (designated MAL) from the seeds of the leguminous plant Maackia amurensis is a potent leukoagglutinin for the mouse lymphoma cell line BW5147 (Wang, W.-C., and Cummings, R. D. (1987) Anal. Biochem. 161,80). We and others have shown that this lectin is a weak hemagglutinin of human erythrocytes (Kawaguchi, T., Matsumoto, I., and Osawa, T. (1974) J. Biol. Chem. 249, 2786). We now report that leukoagglutination by MAL is inhibited by low concentrations of 2,3-sialyllactose (NeuAc alpha 2,3Gal beta 1,4Glc), but it is not inhibited by either 2,6-sialyllactose (NeuAc alpha 2,6Gal beta-1,4Glc), lactose, or free NeuAc. To further study the carbohydrate-binding specificity of this lectin, we investigated the interactions of immobilized MAL with glycopeptides prepared from the mouse lymphoma cell line BW5147 and from purified glycoproteins. We found that immobilized MAL interacts with high affinity with complex-type tri- and tetraantennary Asn-linked oligosaccharides containing outer sialic acid residues linked alpha 2,3 to penultimate galactose residues. Glycopeptides containing sialic acid linked only alpha 2,6 to penultimate galactose did not interact detectably with the immobilized lectin. Our analyses indicate that the interactions of complex-type Asn-linked chains with the lectin are dependent on sialic acid linkages and are not dependent on either the branching pattern of the mannose residues or the presence of poly-N-acetyllactosamine sequences.

Agglutination↗
PubMed1987

IC50 of trifluoperazine and RMI 12330A for the theophylline and phloretin-induced increase in intestinal D-galactose accumulation.

The effect of trifluoperazine and RMI 12330A on D-Galactose accumulation was studied in isolated rat intestinal mucosa. Both drugs inhibited the theophylline and phloretin-induced increase in tissue sugar accumulation in a concentration-dependent fashion, with IC50 values close to 10(-6) M. These findings suggest that calmodulin might mediate the theophylline and phloretin actions on galactose transport in intact rat ileum.

Animals↗
PubMed1986

Presence of glycoproteins in the cell nucleus as shown by radioautographic studies after administration of [3H]fucose and [3H]galactose.

Dorsal root ganglia were removed from adult bullfrogs and incubated with [3H]fucose for intervals from 15 min to 1 h, followed by fixation. Some ganglia were post-incubated in the absence of [3H]fucose for up to 17 h. In additional in vivo experiments, young frogs were injected with [3H]fucose, and killed 30 min or 1 h later, and then ganglia were removed and fixed. Electron microscope radioautographs of the ganglia revealed an intense radioautographic reaction over the nuclei of Schwann and satellite cells as early as 5 min after initial exposure to [3H]fucose. At time intervals up to 2 h after initial exposure to [3H]fucose, the silver grains were evenly distributed over both the periphery and internal regions of the nucleus, while at 18 h they were localized to the cell periphery. In occasional cells, the perinuclear space was expanded in some areas and was the site of reaction. In young rats, injected with [3H]galactose and killed 15 min to 5 h later, electron microscope radioautographs revealed heavy reaction over the nuclei of duodenal villous and crypt columnar cells, in which the grains were evenly distributed over both the peripheral and internal regions. In mitotic cells, grains appeared to be associated with the condensed chromatin of forming chromosomes. These results provide strong evidence that glycoproteins exist in the nuclei of the above cell types and that they are actively renewed. The rapid appearance of nuclear reaction after initial exposure to [3H]fucose or [3H]galactose indicates that either these sugars are added to glycoproteins within the nucleus itself or that they migrate rapidly to this site after having been glycosylated elsewhere.

Animals↗
PubMed1987

Effect of glucose and galactose on red blood cell membrane deformability.

The effect of glucose and galactose on the membrane deformability of red blood cells (RBC) suspended in isotonic solution was determined using micropipette aspiration technique. In this method, a negative pressure was applied to the RBC membrane via a micropipette and the resulting deformation was analyzed using a Kelvin model to yield a membrane elastic modulus E. When glucose concentration was increased from 0 to 0.3 M/dm3 in the extracellular media, E increased seven-fold (p less than 0.0001) with most increase occurring in the 0-0.05 M/dm3 range. The increase in E due to glucose was not completely reversible. The time constant of increase in E was about 14 minutes. Whereas, galactose had no significant effect on the membrane elasticity up to a concentration of 0.3 M/dm3. Increase in the RBC membrane rigidity in the presence of glucose may be due to binding of glucose to the membrane and intracellular proteins. The results obtained may be important for explanation of decrease in tumor blood flow during hyperglycemia.

Animals↗
PubMed1979

Effects of galactose, glucose and fructose on carbohydrate-lipid metabolism.

Doses of glucose, galactose and fructose were administered orally and intravenously, while monitoring the levels of blood glucose, serum insulin, free fatty acids, cholesterol and triglycerides. Blood glucose increases when glucose is administered orally or intravenously, but does not vary significantly with any other sugar. The increase in insulinemia only with oral and intravenous glucose and with oral galactose is in agreement with the participation of intestinal factors in the determination of insulin secretion. The results obtained for free fatty acids with the various sugars may be due to the metabolic properties of each sugar. We found no significant variations in the levels of cholesterol and triglycerides, perhaps because of the short duration of the experiment.

Administration, Oral↗
PubMed1979

Process of iodination of thyroglobulin and its maturation. II. Properties and distribution of thyroglobulin labeled in vitro or in vivo with radioiodine, 3H-tyrosine, or 3H-galactose in rat thyroid glands.

With the aim of obtaining information on the process of iodination of thyroglobulin, the properties and subcellular distribution of thyroglobulin labeled with radioiodine, 3H-tyrosine, or 3H-galactose were studied. The following results were obtained for 17-19S thyroglobulin isolated from rat thyroid lobes labeled in vitro. (a) The effect of sodium dodecyl sulfate (SDS) concentration (0.1-2.0 mM) on the dissociability of the proteins into 12S subunits showed that 3H-labeled, 131I-labeled, and preformed thyroglobulin behaved very differently; their dissociability decreased in that order. In addition, 0.3 mM SDS is most suitable for discriminating among these species. (b) The amount of 0.3 mM SDS-resistant 131I-thyroglobulin increased with the time of incubation of the lobes or with the amount of iodine atoms incorporated by chemical iodination. (c) Digestion of 3H-tyrosine-labeled thyroglobulin showed that 3H-monoiodotyrosine and 3H-diiodotyrosine were present after incubation of the lobes for 180 min. (d) The dissociability of 3H-galactose-labeled 17-19S thyroglobulin was higher than that of 131I-labeled protein, but its elution pattern on DEAE-cellulose chromatography resembled that of the latter. (e) 131I-Thyroglobulin was scarcely found in the incubation medium, although a considerable amount of 19S thyroglobulin was released into the medium during the incubation. As for the lobes, a significant amount of 131I-radioactivity as well as 3H-radioactivity was found in cytoplasmic particulates, especially in fractions containing apical vesicles and rough microsomes. On the other hand, the following results were obtained for 17-19S thyroglobulin isolated from rats injected with 125I. (a) Dissociability of the protein by 0.3 mM SDS and analysis of 125I-iodoamino acids of pronase digest showed that the iodination process was essentially similar to the case of in vitro incorporation, but was faster. (b) The effect of cyclohiximide treatment showed that the relative reduction of 0.3 mM SDS dissociable species was probably due to a shortage of newly synthesized proteins. All the results obtained in the present experiments are compatible with the view that iodine atoms are incorporated selectively into newly synthesized, less iodinated thyroglobulin, and that the iodination occurs intracellularly, at least to a certain degree, after carbohydrate attachment, probably in the apical vesicles. The possibility that iodination also occurs to some extent in the endoplasmic reticulum and in the colloid lumen of thyroglobulin-stimulated thyroids is discussed.

Animals↗