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Biomedical subjects

H Leffler

Publications and source records attributed to H Leffler.

At least 91 records · Page 5Linked to original sources
PubMed1984

Attachment of Streptococcus pneumoniae to human pharyngeal epithelial cells in vitro--mechanism of binding.

To colonize mucosal surfaces and to invade underlying tissues, bacteria need to bind to components of the mucosa. Unattached bacteria are transported away from the surface with the fluid flow. By binding to the nasopharyngeal mucosa, Streptococcus pneumoniae causing otitis media may persist at the site of infection. High binding capacity of the bacterium and increased receptivity of the epithelial cells for attaching bacteria may both contribute to the susceptibility of patients prone to otitis. Thus, epithelial cells from children with frequent episodes of otitis bind attaching bacteria more readily than do cells from age-matched controls. The binding mechanism probably involves bacterial surface proteins and epithelial cell surface glycoconjugate receptors. Evidence is presented that phosphorylcholine, a component of the bacterial surface, as well as epithelial cell receptor analogues, that is, natural or synthetic saccharides analogous to the lactoneoseries of glycolipids, inhibits pneumococcal attachment. Inhibition of bacterial binding in vivo may be a new approach to prophylaxis against otitis media.

Adhesiveness↗
PubMed1983

Identification of an active disaccharide unit of a glycoconjugate receptor for pneumococci attaching to human pharyngeal epithelial cells.

Glycoconjugates containing the disaccharide unit GlcNAc beta 1 leads to 3Gal beta were suggested as receptors for pneumococci adhering to human pharyngeal epithelial cells. The receptor activity was detected both by inhibition of adhesion by an excess of free oligosaccharide and by induction or increase of adhesion after coating of target cells with glycolipid. Studies with free natural and synthetic oligosaccharides identified the disaccharide GlcNAc beta 1 leads to 3Gal beta as one critical binding site. The specificity of recognition was shown inter alia by the lack of inhibitory activity of GlcNAc beta 1 leads to 4Gal beta, which differs only in the linkage of the two sugars. Specific interference with pneumococcal adhesion by administration of soluble receptor sugar may improve our understanding of the role of adhesion in vivo.

Animals↗
PubMed1983

Correlation of P blood group, vesicoureteral reflux, and bacterial attachment in patients with recurrent pyelonephritis.

Bacterial attachment to urinary-tract epithelium is important in the pathogenesis of urinary-tract infection. Most pyelonephritogenic Escherichia coli bind specifically to epithelial-cell receptors, which are glycolipids of the globoseries and also antigens in the P blood-group system. Among 36 girls with recurrent pyelonephritis who did not have vesicoureteral reflux, we found that attaching bacteria were common and the P1 blood-group phenotype was present in 97 per cent, as compared with 75 per cent of 84 age-matched children without urinary-tract infection (P less than 0.01). In 32 girls with recurrent pyelonephritis who had reflux, attaching bacteria were rare, and the frequency of the P1 phenotype was not significantly higher than in controls (82 per cent, P greater than 0.05). In the group of patients with the P1 phenotype, 68 per cent of the urinary bacterial isolates from those without reflux, but only 25 per cent of isolates from those with reflux, bound to globotetraosylceramide, as determined by a receptor-coating technique (P less than 0.001). Our data suggest that, in the absence of reflux, the P1 blood group contributes to susceptibility to recurrent pyelonephritis due to bacteria that bind to the glycolipid receptors of the globoseries. In the presence of reflux, uroepithelial attachment does not seem to confer an advantage to bacteria that infect the kidney.

Adhesiveness↗
PubMed1983

The preparative separation of sialic acid-containing lipids from sulphate group-containing glycolipids from small intestine of different animals. Analysis by thin-layer chromatography and detection of novel species.

Acidic glycolipids (gangliosides and glycolipid sulphates) were purified from non-glycolipid contaminants by silicic acid chromatography of their acetylated derivatives. Acetylation converted gangliosides into non-polar neutral and weakly acidic derivatives. These were separated from acetylated sulphate-containing glycolipids by chromatography on DEAE-cellulose. The fractions thus isolated from small intestine of 7 different animals were analyzed by thin-layer chromatography. This revealed a considerable species-related variation of both gangliosides and sulphoglycolipids. Mass spectrometry demonstrated a novel ganglioside in guinea-pig small intestine and a novel sulphoglycolipid in mouse small intestine.

Acetylation↗
PubMed1983

Target cell specificity of wild-type E. coli and mutants and clones with genetically defined adhesins.

The species, individual and tissue specificity of bacterial binding reactions was studied using wild-type E. coli strains from diarrhoea or urinary tract infection, and derivatives with genetically manipulated adhesins. E. coli J96 and GR12 were isolated from the urine of patients with acute pyelonephritis; E. coli strains expressing the CFAI and II antigens from the stools of patients with diarrhoea. E. coli J96, GR12 and CFAI induced mannose-resistant agglutination of human erythrocytes; E. coli J96 and GR12 in addition carried mannose-sensitive adhesins. Mutants of GR12 with either or both of these adhesins were obtained through chemical mutagenesis. Cloning of 6-8 mdal fragments of chromosomal DNA from J96 into E. coli K12 resulted in expression of pili and binding properties in the previously non-piliated and non-binding strain. Bacterial binding was registered to target cells from different human tissues; small intestinal brush borders, uroepithelial and buccal cells and erythrocytes and was compared between species using rabbit intestinal brush borders, mouse bladder cells and guinea pig erythrocytes. Individual variation was illustrated by agglutination of human P1 erythrocytes and those of blood group p lacking the globoseries glycolipid receptors. Specific recognition of globoseries glycolipid receptors was defined as capacity to agglutinate guinea pig erythrocytes after but not before coating with globotetraosylceramide. Binding specific for mannose-containing receptors was diagnosed by mannose-reversible agglutination of guinea pig erythrocytes. The binding pattern of the wild-type strains was related to the site of infection, i.e. the CFAI and II strains bound to small intestinal brush borders and the pyelonephritogenic E. coli to uroepithelial cells, but not vice versa. The mutants and clones retained the binding properties of the parent/donor both in degree and specificity of binding. Strains with adhesins specific for globoseries glycolipids attached to human uroepithelia, mouse uroepithelial and buccal cells. Within the group of strains with mannose-sensitive adhesins heterogeneity was observed. Strains sharing ability to agglutinate guinea pig erythrocytes to a mannose-reversible manner bound or did not bind to human buccal cells, to human uroepithelial cells and agglutinated or did not agglutinate human erythrocytes. The results demonstrate the usefulness of genetic technology in the study of bacterial binding reactions. The role of pili as adhesins is discussed.

Adhesins, Escherichia coli↗
PubMed1983

Molecular mechanisms of adhesion of Streptococcus pneumoniae to human oropharyngeal epithelial cells.

Adherence of bacteria to mucosal surfaces is an early step in colonization and infection. Streptococcus pneumoniae colonizes the nasopharynx and causes localized and systemic disease. The higher adhesion capacity of strains isolated from patients with otitis as compared to strains from sepsis or meningitis patients indicates that binding to the nasopharyngeal mucosa is important in localized but not in invasive infections. The biochemical basis of the pneumococcal binding to epithelial cells has been investigated. Human nasopharyngeal epithelial cells were mixed with pneumococci, and adherence was determined microscopically. Inhibition of adherence with analogues of epithelial cell receptors was tested by preincubation of pneumococci before the addition of the epithelial cells. Competitive inhibition with glycoconjugates, representing receptor structures on the epithelial cell surface, showed receptor function of saccharides containing the disaccharide GlcNAcbeta1 leads to 3Galbeta-.

Disaccharides↗
PubMed1982

Inhibition of experimental ascending urinary tract infection by an epithelial cell-surface receptor analogue.

It has been shown that the establishment of urinary tract infection by Escherichia coli is dependent on attachment of the bacteria to epithelial cells. The attachment involves specific epithelial cell receptors, which have been characterized as glycolipids. Reversible binding to cell-surface mannosides may also be important. This suggests an approach to the treatment of infections--that of blocking bacterial attachment with cell membrane receptor analogues. Using E. coli mutants lacking one or other of the two binding specificities (glycolipid and mannose), we show here that glycolipid analogues can block in vitro adhesion and in vivo urinary tract infection.

Animals↗
PubMed1982

Studies on differentiating epithelial cells of rat small intestine. Alterations in the lipophilic part of glycosphingolipids during cell migration from crypt villus tip.

Epithelial cells of rat small intestine have been separated into three intervals of different maturity correlated to cell migration from the crypt to the villus tip. The total acid and non-acid glycosphingolipids were isolated and analysed by thin-layer chromatography. The amount of glucosylceramide an N-glycoloylneuraminosyllactosylceramide was higher, while the amount of globotriaosylceramide and tetrahexosylceramide was lower in villus tip cells (more differentiated) compared to crypt cells (less differentiated). In addition to these alterations the lipophilic composition changed, as shown by a comparison by mass spectrometry of permethylated and LiAlH4-reduced, permethylated derivatives of two of the non-acid glycolipid mixtures (crypt cells and villus tip cells). The components of ceramide were mainly trihydroxy 18:0 long-chain base (phytosphingosine) and hydroxy and non-hydroxy fatty acids. The only significant change concerned the fatty acids. In the crypt cell glycolipids the most abundant fatty acid was 20:0 non-hydroxy fatty acid. In the villus tip cells there was a relative increase of hydroxy fatty acids, with the 24:0 species in dominance. This change occurred for most glycolipids, but the fatty acids of glucosylceramide were villus tip-like already in the crypt cells. The blood group A-active tetraglycosylceramide, and probably the hematoside, did not show any alteration in the lipophilic part. The results indicate that the turnover of some glycolipids (or only their lipophilic part) is more rapid than the epithelial cell turnover.

Alkaline Phosphatase↗
PubMed1982

Isolation and partial characterization of blood group A and H active glycosphingolipids of rat small intestine.

Blood group A and H active glycosphingolipids have been isolated from rat small intestine. By mass spectrometry of the permethylated and LiAlH4-reduced permethylated glycolipid derivatives, the A glycolipids were shown to contain four (A-4), six (A-6), and 12 (A-12) sugar residues, respectively. The anomeric structure of the A-4 and A-6 glycolipids was established by proton NMR spectroscopy of the permethylated-reduced derivatives. Acid degradation and gas chromatography were used for analysis of binding positions. The structures of the A-4 and A-6 glycolipids were GalNAcp alpha 1 leads to 3Galp(2 comes from 1Fucp alpha) beta 1 leads to Glcp beta 1 leads to 1Cer and GalNAcp alpha 1 leads to 3Galp(2 comes from 1Fucp alpha) beta 1 leads to 3GlcNAcp beta 1 leads to 4Galp beta 1 leads to 4Glcp beta 1 leads to 1Cer. The third glycolipid (A-12) was a branched dodecaglycosylceramide with two blood group A determinants. The complete structure of this glycolipid has not yet been solved. The blood group A activity was the same for the A-6 and A-12 glycolipids based on an equal number of blood group A determinants, but the activity of the A-4 compound was only about half of the others. The A-6 glycolipid was based on a type 1 (Gal beta 1 leads to 3GlcNAc) carbohydrate chain, thus differing from the already known isomer based on a type 2 chain (Gal beta 1 leads to 4GlcNAc) present in human erythrocyte. The blood group A activity of these two glycolipids was found to be identical. The three rat intestinal blood group A active glycolipids were exclusively located to the mucosa epithelial cells. The blood group H active tri- and pentaglycosylceramides (H-3 and H-5), presumed to be the precursors of the A-4 and A-6 glycolipids, were also identified. A 10-sugar glycolipid (H-10), a possible precursor of A-12, was not detected.

ABO Blood-Group System↗
PubMed1982

Chemical characterization of penta-, hexa-, hepta-, octa-, and nonaglycosylceramides of rat small intestine having a globoside-like terminus.

A novel series of glycosphingolipids has been isolated from the nonepithelial part of rat small intestine. A mixed fraction containing 3 major components corresponding to glycolipids with 5, 6, and 7 sugars and 2 minor components with 8 and 9 sugars was characterized. The structure of the major components was deduced by mass spectrometry and proton NMR spectroscopy of nondegraded permethylated and permethylated-reduced (LiAlH4) derivatives and gas-liquid chromatography of degradation products of native, permethylated, and permethylated-reduced glycolipids. The structures of the penta-, hexa-, and hepta-glycosylceramides were found to be GalNAcp beta 1 leads to (3Galp alpha 1 leads to)2-44Galp beta 1 leads to 4Glcp beta 1 leads to 1Cer. By analogy reasoning, supported by mass spectrometry, the octa- and nonaglycosylceramides were concluded to have 1 and 2 additional internal leads to 3Galp alpha 1 leads to 3 structures, respectively. A pentaglycosylceramide fraction from another rat strain was also isolated. The NMR spectra were in agreement with 2 isomeric structures of which 1 had the internal alpha 1 leads to 4 linkage replaced by an alpha 1 leads to 3 linkage. The fatty acids of all components were nonhydroxy 16:0 to 24:0 acids with the 18:0 homologue as dominating species. The major base was sphingosine and possibly monohydroxy 18:1 base in the larger glycolipids. This is a novel series of structures with a terminal saccharide identical with isoglobotetraoxylceramide (cytolipin R). The glycosyltransferase for the terminal GalNAc beta 1 leads to 3 of cytolipin R may possibly be identical with the enzyme adding the terminal sugar of this novel series. This is supported by the presence in the same tissue of probable precursor glycolipids with 4 to 8 hexoses.

Animals↗
PubMed1982

Glycosphingolipids of rat tissues. Different composition of epithelial and nonepithelial cells of small intestine.

The epithelial cells of rat small intestine (jejunum-ileum) were separated from their supporting stroma (residue). Total nonacid and acid glycosphingolipids were prepared from the two compartments. The acetylated nonacid glycolipids were separated into 10-12 fractions by column chromatography. These were analyzed by chromatographic methods, mass spectrometry, and proton NMR spectroscopy and compared with glycolipids isolated from whole rat small intestine. The sialic acid-containing glycosphingolipids were compared in the same way without subfractionation. At least 37 different glycosphingolipids (different carbohydrate moieties) were found, 23 in the nonepithelial residue and 17 in the epithelial cells of one rat strain. In a second rat strain, another 4 structures were detected. The glycosphingolipids of epithelial cells and nonepithelial residue were distinctly different. Glucosylceramide, lactosylceramide, and globotriaosylceramide were found in both compartments, while isoglobotriaosylceramide was restricted to the nonepithelial residue. A tetrahexosylceramide with a terminal Gal alpha 1 leads to 3 on a globotriaosylceramide core was found in both compartments as were homologues with 1 or 2 additional internal leads to 3Gal alpha 1 leads to units, but homologues with 3 or 4 additional internal Gal were only nonepithelial. Glycosphingolipids with terminal beta-GalNAc were restricted to the nonepithelial residue comprising globotetraosylceramide, isoglobotetraosylceramide, and a series of glycolipids with 5 to 9 sugars having the above-mentioned oligohexosylceramides as core structures. Fucolipids (blood group H) having 3, 5, 6, and 7 sugars and lacking amino sugars, and fucolipids with 5 and 10 sugars containing N-acetylglucosamine were restricted to the epithelial cells. Fucolipids (blood groups H and B) with 5 and 6 sugars containing N-acetylgalactosamine were restricted to the nonepithelial residue. In a 4, 6, and 12 sugars were found in the epithelial cells. N-Glycoloylneuraminosyllactosylceramide was the only ganglioside found in the epithelial cells while N-acetylneuraminosyllactosylceramide was nonepithelial together with gangliosides based on gangliotetraosylceramide and isoglobotetraosylceramide.

Animals↗