Some structural studies on the galactose-containing polysaccharide from bovine placenta.

Polysaccharides were extracted from 8-month-old placenta with aqueous HgCl2. The protein-free material was purified by selective precipitation with Cetavlon in the presence of sodium borate at pH 8.5 and was homogeneous on molecular-sieve chromatography, electrophoresis, and on treatment with Concanavalin A. The preparation contained galactose and glucose as principal monosaccharides with 5 per cent of hexosamines. Methylation studies suggested that D-gluco and D-galactopyranosyl units may be constituents of glucan and galactan respectively which form a molecular aggregate that does not dissociate during the fractionation procedures. After treatment of the fraction with beta-amylase, the proportion of glucose in the polysaccharide diminished, indicating the presence of (1-->4)-linked alpha-D-glucopyranosyl residues. Also, when the fraction was treated with a crude protease having glucosidase activity a residual alpha-D-galactopyranan was isolated and found to contain non-reducing end-groups (30.0 per cent), 3-O-(39.5 per cent) and 3,6-di-O-substituted (30.5 per cent) units. The structure of the galactan was not modified according to methylation data, on removal of the glucosyl component. The polysaccharide fraction (pH 8.5 Cetavlon), isolated from bovine placenta, thus contains a glycogen-like material associated with a galactan as molecular aggregate. This galactan has not been previously recognized in bovine placenta and its occurrence in this organ supports the hypothesis that galactose-containing polysaccharides are involved in foetal development.

Methylation studies of the polysaccharides resulting from sequential Smith-degradations of the galactan from the snail Strophocheilus oblongus.

When the galactan from the albumen glands of the snail Strophocheilus oblongus was submitted to three Smith-degradation, the degraded polysaccharide, isolated in 6% yield, was much more linear. Methylation analysis showed that the Smith-degraded polysaccharide gave an increased percentage of 2,4,6-tri, decreased percentages of 2,3,4,6-tetra-and 2,4-di, and a large variation in the amount of 2,3,4-tri-O-methyl-D-galactose. The sugars in the polysaccharide which result in the formation of 2,3,4,6-tetra- and 2,3,4-tri-O-methyl-D-galactose are destoryed in subsequent degradation procedures. The above observations suggest that the degradation by periodate oxidation proceeds via non-reducing end-groups and though some internal residues that are exposed as the degradation proceeds. As a result of the overall process, new non-reducing end-groups are formed and new (1 leads to 6)-linked D-galactose residues are then exposed. The isolation of glycosides of low molecular weight supports the suggestion that the molecule, in the main, is sequentially degraded from the external layers.

Sugar derivatives and liver mitochondria. I. - Effect of methyl-3,5-di-O-benzyl-2-chloro-2-deoxy-D-arabinofuranoside.

Effect of fifteen sugar derivatives on oxygen uptake and oxidative phosphorylation by liver mitochondria were tested. Full details of the possible mechanism of action of methyl-3,5-di-O-benzyl-2-chloro-2-deoxy-D-arabinofuranoside (VI) was presented. This sugar derivative seems to act as inhibitor of the electron transport in the respiratory chain and as an uncoupler.

Sugar derivatives and liver mitochondria. II. Effect of beta-penta-O-acetyl-D-galactopyranose.

beta-penta-O-acetyl-D-galactopyranose stimulated succinate oxidation in intact liver mitochondria (100%), in broken mitochondria (50%) and in EP1 particles (20%), no effect was observed on purified succinic dehydrogenase. This compound enhances the oxidation of succinate in the presence of Ca2+ and ATP; no effect appeared in the absence of calcium. beta penta-O-acetyl-D-galactopyranose prevents the reversal of Ca2+-induced swelling by EGTA. It seems that this sugar derivative would act, in some way, in the efflux of calcium from mitochondria leading to an accumulation of this bivalent ion in the mitochondria.

Sugar derivatives and liver mitochondria. V - Effect of 6-O-benzoyl-3-deoxy-3-fluoro-1,2-O-isopropylidene-alpha-D-glucofuranose.

Using conventional polarographic and mannometric techniques for assaying oxidative phosphorylation and oxygen uptake in isolated rat liver mitochondria, it was observed a decrease in ADP:O ratio and RC coefficient as a function of treatment with 6-O-benzoyl-3-deoxy-3-fluoro-1,2-O-isopropylidene-alpha-D-glucofuranose, using succinate and alpha-ketoglutarate as substrates. The enzymes activities of different segments of the respiratory chain, indicated an inhibition of NADH-oxidase activity as a result of treatment with 6-O-benzoyl-3-deoxy-fluoro-1,2-O-isopropylidene-alpha-D-glucofuranose. The oxidation of NADH-linked substrates by rat liver mitochondria was depressed by the compound used, while the succinate oxidation was increased.

Estudos de polissacarídeos da placenta bovina em diferentes estágios de gestaçäo / Studies on the polisaccharides from bovine placenta at different stages of pregnancy

Polysaccharides were extracted from bovine placenta at different stages of pregnancy, namely terms of 3, 6, 8, and 9 months, with aqueous HgCl2. Tjhe protein-free material was then purified by selective precipitation with Cetavlon in the presence of sodium borate at pH 8,5. The fractions obtained from 3, 6, 8, and 9 month-old placentas wera designated PL-3, PL-8, and PL-9 respectively and wereeach homobeneous on electrophoresis, molecular-sieve chromatography, and on treatment with Concanavalin A. Polysaccharide contents of the fractions were uniform and acyd hydrolisis provided, in each case, galactose and glucose as principal monosaccharides. G.l.c. analysis of derived alditol acetates showed no variation between the D-glucose: D-galactose ratio obtanined from PL-3 and PL-6, being 68:32, but there was a gradual decreasein the D-glucose content of the PL-8 (58:42) and PL-9 (45:55) fractions