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Biomedical subjects

H Mayer

Publications and source records attributed to H Mayer.

At least 217 records · Page 12Linked to original sources
PubMed1986

Lipopolysaccharide of Providencia rettgeri. Chemical studies and taxonomical implications.

The chemical constitutional analysis of the lipopolysaccharide (LPS) isolated from Providencia rettgeri was carried out. Polyacrylamide gel electrophoresis using sodium dodecylsulfate or sodium deoxycholate showed that the lipopolysaccharide mostly consisted of short sugar chains. The lipid A was precipitated out after mild acid hydrolysis of LPS. From the supernatant degraded polysaccharide and unsubstituted core fractions were isolated. Compositional analysis of the core material revealed the presence of galacturonic acid, galactose, glucose, glucosamine, L-glycero-D-manno-heptose, 3-deoxy-D-manno-octulosonic acid, alanine and phosphorus. Methylation analysis of the core material indicated the presence of terminal units of glucose, galacturonic acid and glucosamine. The chemical structure of the lipid A was elucidated. It constitutes a beta-1,6-glucosamine disaccharide substituted on either side by ester and glycosidically-bond phosphate residues. The ester-bound phosphate was found to be substituted by a 4-amino-4-deoxy-L-arabinosyl residue. The amino groups of the backbone disaccharide are N-acylated by 3-O-(14:0)14:0 and 3-O-14:0. Two hydroxyl groups of the disaccharide are esterified by 3-O-(14:0)14:0 and 3-O-14:0. The taxonomical importance of these structural details will be discussed.

Amino Sugars↗
PubMed1986

Immunocytochemical localization of enterobacterial common antigen in Escherichia coli and Yersinia enterocolitica cells.

Enterobacterial common antigen (ECA) was localized on Lowicryl K4M sections and on ultrathin cryosections by using either a mouse monoclonal antibody or an absorbed rabbit polyclonal immune serum with the corresponding gold-labeled secondary antibodies. Comparable results were obtained with both monoclonal antibody and polyclonal immune serum. Controls with two ECA-negative mutants revealed the ECA specificity of both labeling systems. On Lowicryl K4M sections, good labeling of the outer membrane and of membrane-associated areas in the cytoplasm was obtained. Unexpectedly, however, the ribosome-containing areas of the cytoplasm also showed significant labeling. On ultrathin cryosections, labeling of the cytoplasmic areas was much weaker, although the density of label in the outer membrane was comparable to that obtained with the Lowicryl K4M sections. With the techniques used, it cannot be completely excluded that the appearance of ECA in the cytoplasm is due to displacement of ECA-reactive sites during the preparation procedure.

Antigens, Bacterial↗
PubMed1986

Biosynthesis of enterobacterial common antigen requires dTDPglucose pyrophosphorylase determined by a Salmonella typhimurium rfb gene and a Salmonella montevideo rfe gene.

In group C1 salmonellae, rfe and rff genes linked to the ilv locus specify the synthesis of a glycolipid called the enterobacterial common antigen. In contrast, in group B salmonellae the synthesis requires in addition some of the genes in the rfb cluster, the main genetic determinant of the O side chains of lipopolysaccharide. In an effort to define the biochemical functions of these rfb genes, we looked in Salmonella typhimurium LT2 (group B) for rfb mutants in which the synthesis of both enterobacterial common antigen and the O side chains would be blocked in a manner suppressible by the wild-type rfe cluster of S. montevideo, of group C1. We found one mutant with these characteristics. This rfb mutation affected the activity of dTDPglucose pyrophosphorylase (glucose-1-phosphate thymidylyltransferase, EC 2.7.7.24). Whereas the rfe cluster of S. montevideo contained a gene producing this enzyme activity, there was no evidence for the presence of such a gene in the rfe cluster of group B strains. These results also showed that the synthesis of dTDP-glucose is necessary for the biosynthesis of enterobacterial common antigen; this conclusion fits with the recent demonstration of 4-acetamido-4,6-dideoxy-D-galactose as a component of enterobacterial common antigen (Lugowski et al., Carbohydr. Res. 118:173-181, 1983), because the biosynthesis of the donor of this sugar, dTDP-4-acetamido-4,6-dideoxy-D-galactose, requires dTDPglucose pyrophosphorylase.

Antigens, Bacterial↗
PubMed1986

Regulation by vitamin D metabolites of parathyroid hormone gene transcription in vivo in the rat.

In vitro 1,25-dihydroxycholecalciferol (1,25(OH)2D3) decreased levels of preproparathyroid(preproPTH) hormone mRNA. We have now pursued these studies in vivo in the rat. Rats were administered vitamin D metabolites i.p. and the levels of preproPTH mRNA were determined in excised parathyroid-thyroid glands by blot hybridization. PreproPTH mRNA levels were less than 4% of basal at 48 h after 100 pmol 1,25(OH)2D3, with no increase in serum calcium. Gel blots showed that 1,25(OH)2D3 decreased preproPTH mRNA levels without any change in its size (833 basepair). Microdissected parathyroids after 1,25(OH)2D3 (100 pmol) showed mRNA levels for preproPTH were 40 +/- 8% of controls, but for beta-actin were 100% of controls. The relative potencies of vitamin D metabolites were: 1,25(OH)2D3 greater than 24,25(OH)2D3 greater than 25(OH)D3 greater than vitamin D3. In vitro nuclear transcription showed that 1,25(OH)2D3-treated (100 pmol) rats' PTH transcription was 10% of control, while beta-actin was 100%. These results show that 1,25(OH)2D3 regulates PTH gene transcription. PTH stimulates 1,25(OH)2D3 synthesis, which then inhibits PTH synthesis, thus completing an endocrinological feedback loop.

Animals↗
PubMed1986

Synthesis of three 3-C-hydroxymethylpentoses with the D-ribo-, D-xylo- and L-lyxo-configurations. Identification of the latter with a monosaccharide isolated from phase I Coxiella burnetii lipopolysaccharide.

Three 3-C-hydroxymethylpentoses with the D-ribo-, D-xylo and L-lyxo-configurations, were synthesised via nitromethane addition for the first two and 1,3-dithiane addition for the last one, to appropriate 3-ulose derivatives. 3-C-Hydroxy-methyl-L-lyxose is identical with a monosaccharide component previously isolated from hydrolysates of the phase I Coxiella burnetii lipopolysaccharide.

Chromatography, Gas↗
PubMed1985

Lipopolysaccharides from Yersinia pestis. Studies on lipid A of lipopolysaccharides I and II.

The chemical structure of the lipid A of lipopolysaccharide I and II from Yersinia pestis, strain EV 40, was studied. It consists of a (1 ---- 6), beta-linked D-glucosamine disaccharide which carries two phosphate groups; one phosphate is linked glycosidically with a glucosamine unit, the other one is linked to the non-reducing glucosamine. Various degradation methods combined with 31P nuclear magnetic resonance spectroscopy showed that the ester-bound phosphate group is linked to a 4-aminoarabinosyl residue and the glycosidically linked phosphate group is linked to a D-arabinofuranosyl residue in lipopolysaccharide II and to the phosphorylethanolamine in lipopolysaccharide I. The hydroxyl groups of the disaccharide are acylated by dodecanoic, hexadecenoic, 3-hydroxytetradecanoic and 3-dodecanoyloxytetradecanoic acids. The amino groups of the disaccharide carry 3-hydroxytetradecanoic and 3-dodecanoyloxytetradecanoic acids. In addition smaller amounts of 3-tetradecanoyloxyltetradecanoic and 3-hexadecanoyloxytetradecanoic acids are present in ester linkage.

Acetylation↗
PubMed1985

3-C-branched aldoses in lipopolysaccharide of phase I Coxiella burnetii and their role as immunodominant factors.

Mild acid hydrolysis with 1% acetic acid (100 degrees C, 15-60 min) of lipopolysaccharide (LPS) isolated from Coxiella burnetii phase I cells leads to a drastic decrease in its serological reactivity as shown by the passive hemolysis test. This decrease in reactivity occurs parallel or even prior to the cleavage of LPS into free lipid A and the polysaccharide moiety. During this mild hydrolysis two unusual sugars (X and Y) are released from the LPS, which were obtained in pure state by thin-layer chromatography. Analysis of their alditol acetate derivatives by gas chromatography/mass spectrometry revealed that sugar X is a 6-deoxy-3-C-methyl-hexose and sugar Y a 3-C-(hydroxymethyl)-pentose. Using a range of authentic standards and different thin-layer and gas chromatographic conditions, X could be recognized as 6-deoxy-3-C-methyl-gulose (virenose), very probably as the L form of this sugar (L-virenose). Y has been identified as 3-C-(hydroxymethyl)-lyxose (dihydrohydroxystreptose) by comparing it with newly synthesized 3-C-(hydroxymethyl)-pentoses (Dahlman, O., Garegg, P. J., Mayer, H., Schramek, S., unpublished results). Both branched sugars are (at least partially) in terminal positions since methylation analysis of LPS afforded (mainly) their permethylated derivatives. This analysis further showed virenose to be linked in C. burnetii phase I LPS as pyranose and dihydro-hydroxystreptose as furanose. The terminal linkage and the chemical nature of X and Y are in accordance with the observed acid-lability of the serological determinants.

Carbohydrates↗
PubMed1985

[Pathogenesis of retinopathy in acute pancreatitis].

Several cases of ischemic damage to the retina associated with acute pancreatitis have been reported since 1975. The retinal disease is said to be caused by fat embolism of retinal vessels. However, since occlusions of blood vessels do not adequately explain the severe morphological changes and malfunctions of the retina, other etiological influences or a combination of them must be considered for this ophthalmological complication.

Acute Disease↗
PubMed1985

Biosynthesis of enterobacterial common antigen.

Cultures of Salmonella typhimurium pulse-labeled with N-acetyl-D-[3H]glucosamine ([3H]GlcNAc) incorporated isotope into a GlcNAc-linked lipid that was tentatively identified as GlcNAc-pyrophosphorylundecaprenol. The incorporation of [3H]GlcNAc into this compound was abolished when cells were pulse-labeled in the presence of the antibiotic tunicamycin. Tunicamycin also abolished the in vivo synthesis of the haptenic form of enterobacterial common antigen (ECA) in S. typhimurium as determined by the passive hemagglutination test. These data indicated that the synthesis of the GlcNAc-linked lipid is related to ECA synthesis. Support for this conclusion was provided by the following observations. Cultures of Escherichia coli and S. typhimurium incorporated [3H]GlcNAc into cell envelope components that migrated as a homologous series of polymers when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The [3H]GlcNAc-labeled polymers were not detected in mutants of E. coli and S. typhimurium defective in ECA synthesis due to lesions in either the rfe or rff gene clusters. These polymers were identified as ECA based on Western blot analyses employing anti-ECA monoclonal antibody. The incorporation of [3H]GlcNAc into ECA polymers was abolished by tunicamycin when the drug was added to cultures to give a minimum concentration of 3 micrograms/ml. In addition, pulse-chase experiments provided evidence for a precursor-product relationship between the GlcNAc-linked lipid and ECA. These results strongly suggest that the GlcNAc-linked lipid is involved in the biosynthesis of ECA in a manner analogous to the role of carrier lipid in the biosynthesis of O-antigen and peptidoglycan.

Acetylglucosamine↗
PubMed1985

Genetic location of genes encoding enterobacterial common antigen.

A new rff mutation (rff-726) of Escherichia coli is described which affects the biosynthesis of the enterobacterial common antigen. This mutation was detected in an rfe-defective strain. A Tn10 insertion near the rfe locus was isolated to facilitate further mapping. Both mutations rfe and rff were mapped by transduction with bacteriophage P1, giving the gene order ilv rfe rff uvrD metE. The F' factor F14 was able to complement both mutations rfe and rff, whereas the F' factor F16 could complement the rfe but not the rff mutation. The rff mutation did not affect the biosynthesis of N-acetyl-D-mannosaminuronic acid, as the previously described rff mutations in Salmonella typhimurium do (H. C. Lew, H. Nikaido, and P. H. Mäkelä, J. Bacteriol. 136:227-233, 1978), and also did not affect the biosynthesis of other enterobacterial common antigen components; however, the biosynthesis of the complete enterobacterial common antigen molecule was blocked.

Antigens, Bacterial↗
PubMed1985

New approach to area image analysis of Scheimpflug photos of the anterior eye segment.

Based on the Scheimpflug principle, the rotating photo slitlamp Topcon SL 45 can produce photos of a high depth of focus from a slit beam through the anterior eye segment. The Scheimpflug photos are digitized with a special semiconductor camera. A new method, using the digital picture subtraction, is presented. This method is suited for experimental and clinical studies dealing with the development of the lens opacities.

Anterior Eye Segment↗
PubMed1985

Structure of the penicillin acylase gene from Escherichia coli: a periplasmic enzyme that undergoes multiple proteolytic processing.

Penicillin acylase is processed from a 90-kD precursor through the cleavage of a leader peptide and two further endopeptidase cleavages to yield an enzyme that contains a 22-kD (or 23-kD) and a 65-kD subunit. The endopeptidase cleavages require an intact carboxy terminus. This type of processing appears to be unique for a prokaryotic enzyme, having its most closely related analog in the synthesis and processing of preproinsulin and other eukaryotic hormones.

Amidohydrolases↗
PubMed1985

Immunoelectron microscopic localization of the restriction endonuclease EcoRI in Escherichia coli BS 5.

Purified restriction endonuclease EcoRI isolated from Escherichia coli BS 5 was used for the production of enzyme-specific IgG antibodies in rabbits. For enzyme localization experiments, paraformaldehyde-glutaraldehyde-fixed cells were embedded and polymerized by a low-temperature procedure using Lowicryl K4M. The immuno electron microscopic protein A-gold technique and an immuno-gold method revealed that 70% of the enzyme-specific labeling were located in the cell envelope whereas 30% were found in the cytoplasm. In metal-shadowed preparations, no indications for the presence of the enzyme could be found on the cell surface; however, on the surface of cell protoplasts enzyme specific labeling could be detected. The results indicate the presence of the major amount of EcoRI in the periplasmic space of the cell where it might be loosely bound or even freely diffusible.

DNA Restriction Enzymes↗
PubMed1984

The structure of the polysaccharide moiety of Rhodopseudomonas sphaeroides ATCC 17023 lipopolysaccharide.

The chemical structure of the polysaccharide moiety of the lipopolysaccharide Rhodopseudomonas sphaeroides ATCC 17023 was established. Mild acetic acid hydrolysis of isolated lipopolysaccharide, followed by preparative high-voltage paper electrophoresis afforded three oligosaccharides. They were characterized by chemical and physicochemical studies to be: GlcA(alpha 1----4)dOclA8P, Thr(6') GlcA(alpha 1----4)GlcA and GlcA(alpha 1----4)dOclA, where GlcA is D-glucuronic acid and dOc1A is 3-deoxy-D-manno-octulosonic acid. Carboxyl-reduction of the lipopolysaccharide followed by acid hydrolysis gave a trisaccharide: GlcA(alpha 1----4)Glc(alpha 1----4)Glc, showing the presence of three residues of glucuronic acids in the O-specific chain and indicating that only two of them are reducible by NaBH4. The linkage between the polysaccharide and lipid A was shown to be through a single 1,4-linked residue of dOc1A attached by a 2,6'-linkage to the lipid A moiety.

Chemical Phenomena↗
PubMed1984

Eight new restriction endonucleases fröm Herpetosiphon giganteus--divergent evolution in a family of enzymes.

Characterization of eight restriction endonucleases isolated from five strains of Herpetosiphon giganteus is described. HgiCI from strain Hpg9 recognizes and cleaves the degenerate sequence: GGPyPuCC, producing 5'-hexanucleotide protruding ends. Endonucleases HgiBI, HgiCII and HgiEI are isoschizomers of AvaII; HgiCIII and HgiDII are isoschizomers of SalI; and HgiDI and HgiGI are isoschizomers of AcyI. Based upon their closely related and in part overlapping recognition specificities a close evolutionary relationship is proposed for all known Hgi restriction endonucleases.

Base Sequence↗