Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “GLUCOSAMINE”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,387 records · Page 77Linked to original sources
PubMed1990

N-acetyl-D-glucosamine countertransport in lysosomal membrane vesicles.

Countertransport of GlcNAc was examined in membrane vesicles prepared from rat liver lysosomes which had been lysed by exposure to 5 mM-methionine methyl ester. These vesicles have a random orientation, have intact ATP-dependent acidification and are largely free of soluble hydrolases. Vesicular volume (24.69 +/- 4.51 microliters/mg of protein) was greater than that of lysosomes (3.02 +/- 0.56 microliters/mg of protein), corresponding to a doubling of diameter. Characteristics of GlcNAc transport in vesicles (Km = 1.3 mM) were similar to those observed in intact lysosomes (Km = 4.4 mM). Sulphation or phosphorylation of the substrate resulted in loss of recognition by the carrier. Hydroxyl group orientation at multiple positions did not appear to be critical, whereas orientation of the acetyl group appeared to have a fundamental role in recognition by the carrier. Based on these criteria, phenyl isothiocyanate-GlcNAc (PITC-GlcNAc) was identified as a possible substrate for transport. Under mild conditions, PITC-GlcNAc reversibly inhibited GlcNAc countertransport in lysosomes and vesicles. This and other modified substrates may be of value in identification of the GlcNAc/GalNAc lysosomal transporter. Lysosomal membrane vesicle preparation is a technique that should be useful for the study of other lysosomal transport systems.

Acetylglucosamine↗
PubMed1999

Discordant effects of glucosamine on insulin-stimulated glucose metabolism and phosphatidylinositol 3-kinase activity.

The impact of increased GlcN availability on insulin-stimulated p85/p110 phosphatidylinositol 3-kinase (PI3K) activity in skeletal muscle was examined in relation to GlcN-induced defects in peripheral insulin action. Primed continuous GlcN infusion (750 micromol/kg bolus; 30 micromol/kg.min) in conscious rats limited both maximal stimulation of muscle PI3K by acute insulin (I) (1 unit/kg) bolus (I + GlcN = 1.9-fold versus saline = 3.3-fold above fasting levels; p < 0.01) and chronic activation of PI3K following 3-h euglycemic, hyperinsulinemic (18 milliunits/kg.min) clamp studies (I + GlcN = 1.2-fold versus saline = 2.6-fold stimulation; p < 0.01). To determine the time course of GlcN-induced defects in insulin-stimulated PI3K activity and peripheral insulin action, GlcN was administered for 30, 60, 90, or 120 min during 2-h euglycemic, hyperinsulinemic clamp studies. Activation of muscle PI3K by insulin was attenuated following only 30 min of GlcN infusion (GlcN 30 min = 1.5-fold versus saline = 2.5-fold stimulation; p < 0.05). In contrast, the first impairment in insulin-mediated glucose uptake (Rd) developed following 110 min of GlcN infusion (110 min = 39.9 +/- 1.8 versus 30 min = 42.8 +/- 1.4 mg/kg.min, p < 0.05). However, the ability of insulin to stimulate phosphatidylinositol 3,4, 5-trisphosphate production and to activate glycogen synthase in skeletal muscle was preserved following up to 180 min of GlcN infusion. Thus, increased GlcN availability induced (a) profound and early inhibition of proximal insulin signaling at the level of PI3K and (b) delayed effects on insulin-mediated glucose uptake, yet (c) complete sparing of insulin-mediated glycogen synthase activation. The pattern and time sequence of GlcN-induced defects suggest that the etiology of peripheral insulin resistance may be distinct from the rapid and marked impairment in insulin signaling.

Animals↗
PubMed2005

The incorporation of glucosamine into enterobacterial core lipopolysaccharide: two enzymatic steps are required.

The core lipopolysaccharide (LPS) of Klebsiella pneumoniae is characterized by the presence of disaccharide alphaGlcN-(1,4)-alphaGalA attached by an alpha1,3 linkage to l-glycero-d-manno-heptopyranose II (ld-HeppII). Previously it has been shown that the WabH enzyme catalyzes the incorporation of GlcNAc from UDP-GlcNAc to outer core LPS. The presence of GlcNAc instead of GlcN and the lack of UDP-GlcN in bacteria indicate that an additional enzymatic step is required. In this work we identified a new gene (wabN) in the K. pneumoniae core LPS biosynthetic cluster. Chemical and structural analysis of K. pneumoniae non-polar wabN mutants showed truncated core LPS with GlcNAc instead of GlcN. In vitro assays using LPS truncated at the level of d-galacturonic acid (GalA) and cell-free extract containing WabH and WabN together led to the incorporation of GlcN, whereas none of them alone were able to do it. This result suggests that the later enzyme (WabN) catalyzes the deacetylation of the core LPS containing the GlcNAc residue. Thus, the incorporation of the GlcN residue to core LPS in K. pneumoniae requires two distinct enzymatic steps. WabN homologues are found in Serratia marcescens and some Proteus strains that show the same disaccharide alphaGlcN-(1,4)-alphaGalA attached by an alpha1,3 linkage to ld-HeppII.

Acetylation↗
PubMed2003

Expression of glucosamine trisaccharides on the rat uterine surface is altered by clomiphene citrate. III. Relationship with implantation regimes and pregnancy.

The present study further elucidates the complex effects of a commonly-prescribed fertility drug upon a target organ in an animal model. In the human condition, its effects are rarely observed without the influence of endogenous ovarian hormones. The aim of the study was to investigate how the administration of a single dose of clomiphene citrate (CC) given prior to an implantation-priming sequence of ovarian hormones would affect the expression of surface oligosaccharides and membrane architecture of uterine epithelium. Ovariectomized rats were given a single dose of either 0.25 mg or 1.25 mg of CC prior to a hormone-priming regime of progesterone (P4) for 3 days with a single additional administration of oestradiol 17beta (E2) on day 3. Animals were killed 24 h after final treatment. Uterine tissue was labelled with the lectin Phytolacca americana conjugated with avidin, subsequently labelled with biotinylated ferritin and prepared for transmission electron microscopy. Results indicate that CC, when administered prior to the implantation hormone-priming regime, is able to act as a super oestrogen and upregulates expression of oligosaccharides on the plasma membrane surface and increases the density and length of microvilli on the surface of the cells when compared with other treatment regimes. Understanding of the effects of CC at the uterine level at the time of implantation enables manipulation of uterine receptivity to control fertility and to improve the outcome of assisted reproductive procedures.

Animals↗
PubMed1957

The crystal structure of alpha-chitin (poly-N-acetyl-D-glucosamine).

A detailed model for the crystal structure of the fibrous polysaccharide chitin is proposed. The structure determination has been carried out by using an optical analogue instrument which proved to be an adequate and rapid tool for the derivation of Fourier transforms, signs of amplitudes and the production of optical Fourier syntheses. The new model of chitin accounts properly for known chemical and physical properties, including the infrared absorption as well as for x-ray data, but because of the limited resolution of the diffraction patterns it can only be regarded as a good approximation. The stereochemical configuration of the polysaccharide chains has certain implications for the structure of cellulose.

Acetylglucosamine↗
PubMed1988

Biology of Giardia lamblia. Detection of N-acetyl-D-glucosamine as the only surface saccharide moiety and identification of two distinct subsets of trophozoites by lectin binding.

Lectins and glycosidases of known sugar specificity were used as probes to analyze the surface carbohydrate moieties of G. lamblia trophozoites and in particular to determine whether chitin or oligomeric D-GlcNAc is present in the trophozoite form of the parasite as well as on the cyst. Of 13 lectins with varying sugar specificity, only D-GlcNAc-specific lectins bound specifically to the trophozoite surface as determined by light microscopy and EM. A striking finding was the identification of two distinct subsets of trophozoites, distinguished by reactivity with WGA and detected by light microscopy and EM as well as by flow cytometry. Unlike the cyst wall, the trophozoite D-GlcNAc residues were resistant to chitinase treatment. In contrast N-acetyl-beta-D-glucosaminidase abolished WGA binding suggesting that the lectin binds to terminal beta-linked D-GlcNAc residues. These residues were identified as being present on surface glycoproteins by Western blotting of parasite membrane proteins using WGA as a probe. This study identifies D-GlcNAc as the only saccharide moiety detectable by lectin binding on the surface of G. lamblia trophozoites and demonstrates that in contrast to the cyst, chitin is not present in the trophozoite. In addition two distinct subsets of trophozoites were identified based on reactivity with WGA and may represent varying stages of differentiation from trophozoite to cyst.

Acetylglucosamine↗