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M McNeil

Publications and source records attributed to M McNeil.

At least 55 records · Page 3Linked to original sources
PubMed1989

Plasma desorption mass spectrometric analysis of mycobacterial glycolipids.

Mycobacteria are characterized by species- or type-specific glycolipid antigens. These are generally of the following three types: the trehalose-containing, acylated lipooligosaccharides (LOS), the C-mycoside glycopeptidolipids (GPL), and the phenolic glycolipids (PGL). To date, convenient mass spectrometric analysis of the intact form of these complex glycolipids has proved to be difficult. The successful plasma desorption mass spectrometric analysis of intact mycobacterial glycolipids of the LOS, GPL, and PGL types is now reported, allowing location of the acyl residues and providing oligosaccharide sequence and molecular weight information.

Chemical Phenomena↗
PubMed1989

Hospital outreach community-based health care: the case of Chogoria, Kenya.

This article presents an analysis of the community health activities of Chogoria Hospital, Kenya, as they evolved from a typical 'outreach' programme to a heavily community-based one, and the factors that contributed to this conversion. Factors considered include family planning, being the central theme of the programme since its inception, financing, and the impact of the programme is illustrated with data from an extensive evaluation carried out in 1985. The question of long-term financial viability is addressed, contrasting the desired self-sufficiency with the need and extent of donor contributions and finally a number of key factors are listed that may have been important to the success of the programme.

Child Health Services↗
PubMed1989

Microbial glycolipids: possible virulence factors that scavenge oxygen radicals.

Two important pathogens of developing countries, Mycobacterium leprae, the etiologic agent of leprosy, and Leishmania donovani, the protozoal parasite that causes kalaazar, persist in the human host primarily in mononuclear phagocytes. The mechanisms by which they survive in these otherwise highly cytocidal cells are presently unknown. Since the best understood cytocidal mechanism of these cells is the oxygen-dependent system that provides lethal oxidants including the superoxide anion (O2-), hydrogen peroxide (H2O2), hydroxyl radical (OH), and singlet oxygen (1O2), we sought specific microbial products of these organisms that might enable them to elude oxidative cytocidal mechanisms. Phenolic glycolipid I of M. leprae and lipophosphoglycan of L. donovani are unique cell-wall-associated glycolipids produced in large amounts by the organisms. In this study, phenolic glycolipid I derivatives and lipophosphoglycan were examined for their ability to scavenge potentially cytocidal oxygen metabolites in vitro. Electron spin resonance and spin-trapping indicate that phenolic glycolipid I derivatives and lipophosphoglycan are highly effective in scavenging hydroxyl radicals and superoxide anions. The results suggest that complex glycolipids and carbohydrates of intracellular pathogens that can scavenge oxygen radicals may contribute to their pathogenicity and virulence.

Animals↗
PubMed1989

Structure and function of mycobacterial glycolipids and glycopeptidolipids.

Earlier work from this and other laboratories has revealed the presence within Mycobacterium spp. of three classes of glycolipid antigens which we have called the glycopeptidolipids, the lipooligosaccharides and the phenolic glycolipids. Representative structures of each from different species and sub-species have been proposed. More recently, new variants of these antigens and older structures have been analyzed by Fourier transform infrared, NMR, particularly at high temperatures, and, most notably, by fast atom bombardment and Californium desorption mass spectrometry. Extraordinary novelty and diversity were revealed, particularly at the distal non-reducing end of the oligosaccharide chains, marked by the presence of new branched-chain sugars, amino sugars and sugar acids. These epitopes and monoclonal antibodies to them have been used for the critical identification of mycobacteria. In addition, the pure antigens are the basis of specific serological tests for various mycobacterioses. The resurgence of interest in "atypical" mycobacteria stems from their occurrence as opportunistic pathogens in many patients with acquired immunodeficiency syndrome, although they have long been associated with pulmonary and other organ infections. Foremost among these mycobacteria are serovars of the Mycobacterium avium-Mycobacterium intracellulare complex (the M. avium complex). The surface antigens which differentiate these serovars are glycopeptidolipids, related to "mycoside C" and, accordingly, composed of a glycosylated lipopeptide "core", fatty acyl-D-Phe-D-alloThr-D-Ala-L-acanyl-O- (3,4-di-O-methyl-alpha-L-rhamnopyranoside), to which a haptenic oligosaccharide is linked at the threonine substituent; this oligoglycosyl unit is the source of type specificity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Further novel amido sugars within the glycopeptidolipid antigens of Mycobacterium avium.

The individual serovars of the Mycobacterium avium complex, a source of serious and persistent infections in individuals with underlying immune deficiencies, also present an extraordinary set of novel sugar epitopes as part of their type-specific glycopeptidolipid surface antigens. Californium desorption-mass spectrometry has been successfully applied to the holistic glycopeptidolipid antigen of M. avium serovar 12 and its per-O-acetyl derivative, to arrive at the following structure, of molecular mass 1876: (Sequence: see text). The pentasaccharide hapten, released as the tetraglycosyl alditol, was subjected to methylation analysis, absolute configurational analysis, 1H NMR and fast atom bombardment-mass spectrometry to arrive at the structure: 4-(2'-Hydroxy) propionamido-4,6-dideoxy-3-O-Me-Glcp (beta 1----3)-4-O-Me-L-Rhap (alpha 1----3)-L-Rhap (alpha 1----3)-L-Rhap (alpha 1----2)-6-deoxytalitol. Two-dimensional proton correlation spectroscopy was also applied to determine the configuration of the unique distal segment of the oligosaccharide unit. The significance of this structure in the context of the fully elucidated structures of the antigens from 12 of the 31-member M. avium complex is discussed.

Antigens, Bacterial↗
PubMed1988

N-formylkansosaminyl-(1----3)-2-O-methyl-D-rhamnopyranose: the type-specific determinant of serovariant 14 of the Mycobacterium avium complex.

Significant occurrences of pulmonary and disseminated infections due to "atypical" mycobacteria have again focused attention on the Mycobacterium avium serocomplex. An examination of the major surface glycopeptidolipid antigen of one of the more prominent and one of the first described serovariants, the Boone strain (serovariant 14), has shown that it is characterized by a unique terminal disaccharide unit, N-formylkansosaminyl-(1----3)-2-O-methyl-D-rhamnopyranose. The structure of the entire oligoglycosyl hapten is N-formylkansosaminyl-(1----3)-2-O-methyl-alpha-D-rhamnopyranosyl-( 1----3)-2-O- methyl-alpha-L-fucopyranosyl-(1----3)-alpha-L-rhamnopyranosyl-(1----2)-6 -deoxy- L-talose. We had previously described a 4,6-dideoxy-2-O-methyl-3-C-methyl-4-(2-methoxy propanamido)-L-mannopyranose (an N-acylkansosamine) as the characteristic sugar of the trehalose-containing lipo-oligosaccharide antigens of strains of Mycobacterium kansasii. Thus, a derivative of this sugar is now found to occur in other mycobacteria as part of other antigens. The other distinguishing feature of the structure is the presence of D-rhamnopyranose, which occurs only sparingly in Nature.

Antigens, Bacterial↗
PubMed1988

Trehalose-containing lipooligosaccharide antigens of Mycobacterium sp.: presence of a mono-O-methyltri-O-acyltrehalose "core".

We have described the surface antigens of Mycobacterium kansasii as trehalose-containing lipooligosaccharides (LOS) which at the nonreducing "epitope" end bear a unique amino sugar containing diglycosyl unit, whereas the putative reducing end consists of an acylated alpha, alpha-trehalose-containing tetraglucosyl "core" [Hunter, S. W., Jardine, I., Yanagihara, D. L., & Brennan, P. J. (1985) Biochemistry 24, 2798-2805]. The presence of a new variation on this core, in Mycobacterium szulgai, is now reported, ----3)beta-D-Glcp-(1----6)alpha-D-Glcp(1----1)3,4,6-tri-O-acyl-2-O- Me-alpha-D-Glcp, representing the first example of an O-methyltrehalose unit in nature. The simplest of the LOS class of glycolipids in M. szulgai was defined as alpha-L-2-O-Me-Fucp(1----3)alpha-L-Rhap(1----3)alpha-L-Rh ap(1----3) beta-D-Glcp(1----6)alpha-D-Glcp(1----1)3,4,6-tri-O-acyl-2-O-Me-alpha-D-G lcp. Further glycosylation of this nonantigen, by an incompletely defined 6-deoxyhexosyl residue, confers specific antigenicity on the organism. Thus, these extraordinary structures, in a manner analogous to the better known lipopolysaccharides from rough variants of Enterobactericiae, are highly amphipathic and display variability not only in the immunogenic, distal region but also in the "invariant" lipophilic core. The contribution of these glycolipids to the hydrophobic barrier, the pseudo outer membrane of mycobacteria, is discussed.

Acylation↗
PubMed1988

Immunological significance of Mycobacterium leprae cell walls.

Cell walls of Mycobacterium leprae, prepared by differential solvent extraction, were shown to contain arabinogalactan, mycolates, and peptidoglycan. In addition, amino acid analysis revealed the unexpected presence of large amounts of protein that retained potent immunological reactivity. Purified cell walls stimulated proliferation of T cells from tuberculoid, but not from lepromatous leprosy, patients and elicited delayed-type hypersensitivity skin reactions in guinea pigs and patients sensitized to M. leprae. Analysis of the precursor frequency of antigen-reactive human peripheral T cells revealed that as many cells (approximately equal to 1/6000) proliferate to antigen contained in cell walls as to intact M. leprae. Sequential removal of mycolates and arabinogalactan resulted in a large peptidoglycan-protein complex that retained all the immunological activity. This immunological reactivity and the inherent protein were destroyed by proteolysis. Thus, cell wall protein is a major contributor to cell-mediated immune reactivity to this pathogenic mycobacterium.

Amino Acids↗
PubMed1987

Demonstration that the galactosyl and arabinosyl residues in the cell-wall arabinogalactan of Mycobacterium leprae and Mycobacterium tuberculosis are furanoid.

By a complex process involving methylation, partial hydrolysis with acid, reduction with sodium borodeuteride, ethylation, further hydrolysis and reduction, and subsequent capillary gas-liquid chromatography-mass spectrometry of the derived alditol acetates, it was established that the arabinogalactans of Mycobacterium leprae and Mycobacterium tuberculosis contain arabinofuranyosyl and galactofuranosyl residues exclusively. Thus, the covalently bound, highly immunogenic arabinogalactan of mycobacteria, and presumably of other actinomycetes, is highly unusual, in that all of the glycosyl residues are in the furanoid form. Furthermore, by establishing that the galactofuranosyl residues are either 5-, 6-, or 5,6-linked, their linkage pattern was established, and the literature is corrected on this point.

Arabinose↗
PubMed1987

Structure of a new hexasaccharide from the coaggregation polysaccharide of Streptococcus sanguis 34.

The major constituent of a coaggregation polysaccharide from Streptococcus sanguis 34 is a hexasaccharide, isolated as the alditol. The proposed structure is alpha-D-GalpNAc-(1----3)-beta-L-Rhap-(1----4)-beta-D-Glcp-(1----6) -beta-D-Galf- (1----6)-beta-D-GalpNAc-(1----3)-D-Galol, based upon g.l.c.-m.s. of alditol acetates and partially methylated alditol acetates, f.a.b.-m.s., 1H-n.m.r. spectroscopy, g.l.c.-m.s. of trimethylsilylated (+)- and (-)-2-butyl glycosides, and cleavage by alpha-N-acetylgalactosaminidase. The structural deduction was facilitated by cleavage of the hexasaccharide at the furanoside linkage by 48% hydrogen fluoride, and reduction of the product, to yield alpha-D-GalpNAc-(1----3)-beta-L-Rhap-(1----4)-beta-D-Glcp-(1----6) -D-Galol.

Carbohydrate Conformation↗
PubMed1987

Structure and antigenicity of the specific oligosaccharide hapten from the glycopeptidolipid antigen of Mycobacterium avium serotype 4, the dominant Mycobacterium isolated from patients with acquired immune deficiency syndrome.

A large number of patients with acquired immune deficiency syndrome develop disseminated infections due to member serotypes of the Mycobacterium avium complex. Seroagglutination on 181 such isolates followed by enzyme-linked immunosorbent assay and thin layer chromatography of the type-specific glycopeptidolipid (GPL) antigens demonstrated that the majority of serotypes were M. avium serotype 4. The specific GPL of serotype 4 was isolated in both the native, acetylated, and the deacetylated forms and its oligosaccharide hapten released as the oligosaccharide alditol by reductive beta-elimination. A comprehensive structural analytical approach developed for more complex carbohydrates was applied to the oligosaccharide alditol in order to reveal glycosyl and glycosyl-linkage composition, sequence arrangements, ring forms, and enantiomeric and anomeric configurations. The structure of the triglycosyl alditol was established as, 4-O-Me-L-Rhap-(alpha 1----4)-2-O-Me-L-Fucp-(alpha 1----3)-L-Rhap- (alpha 1----2)-6-deoxytalitol, in which the nonreducing-end disaccharide unit is unique to serotype 4. The native GPL antigen is diacetylated, presumably at other than the terminal disaccharide, since the antigenicity of both the acetylated and deacetylated antigens are comparable. The structure of the epitope of the type-specific antigen of serotype 4 will serve as the basis for synthetic antigen probes and the target for the monoclonal antibodies required to trace the origins in the environment of the infectious agent and study the epidemiology of human infections.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Structure of Plant Cell Walls : XIX. Isolation and Characterization of Wall Polysaccharides from Suspension-Cultured Douglas Fir Cells.

The partial purification and characterization of cell wall polysaccharides isolated from suspension-cultured Douglas fir (Pseudotsuga menziesii) cells are described. Extraction of isolated cell walls with 1.0 m LiCl solubilized pectic polysaccharides with glycosyl-linkage compositions similar to those of rhamnogalacturonans I and II, pectic polysaccharides isolated from walls of suspension-cultured sycamore cells. Treatment of LiCl-extracted Douglas fir walls with an endo-alpha-1,4-polygalacturonase released only small, additional amounts of pectic polysaccharide, which had a glycosyl-linkage composition similar to that of rhamnogalacturonan I. Xyloglucan oligosaccharides were released from the endo-alpha-1,4-polygalacturonase-treated walls by treatment with an endo-beta-1,4-glucanase. These oligosaccharides included hepta- and nonasaccharides similar or identical to those released from sycamore cell walls by the same enzyme, and structurally related octa- and decasaccharides similar to those isolated from various angiosperms. Finally, additional xyloglucan and small amounts of xylan were extracted from the endo-beta-1,4-glucanase-treated walls by 0.5 n NaOH. The xylan resembled that extracted by NaOH from dicot cell walls in that it contained 2,4- but not 3,4-linked xylosyl residues. In this study, a total of 15% of the cell wall was isolated as pectic material, 10% as xyloglucan, and less than 1% as xylan. The noncellulosic polysaccharides accounted for 26% of the cell walls, cellulose for 23%, protein for 34%, and ash for 5%, for a total of 88% of the cell wall. The cell walls of Douglas fir were more similar to dicot (sycamore) cell walls than to those of graminaceous monocots, because they had a predominance of xyloglucan over xylan as the principle hemicellulose and because they possessed relatively large amounts of rhamnogalacturonan-like pectic polysaccharides.

Journal Article↗
PubMed1987

Location of acyl groups of trehalose-containing lipooligosaccharides of mycobacteria.

A variant of a Mycobacterium sp. originating in a patient with Crohn's disease, but not necessarily implicated in the disease, provided a simple version of a newer class of species-specific surface glycolipids, the trehalose-containing lipooligosaccharides. A combination of high-resolution 1H nuclear magnetic resonance, methylation, ethylation, and absolute configurational analysis established the structure of the oligosaccharide unit as beta-D-Glcp(1----3)-alpha-L-Rhap(1----3)-alpha-D-Glcp(1----1)-alph a-D-Glcp (where Glc is glucose, Rha is rhamnose, and p is pyranosyl), and gas chromatography-electron impact mass spectrometry allowed identification of the fatty acyl esters as primarily 2,4-dimethyltetradecanoate. The relative simplicity of the glycolipid combined with the application of a mild methylation procedure and californium-252 plasma desorption mass spectrometry allowed recognition of three such acyl residues on the 3-, 4-, and 6-hydroxyl positions of the terminal glucosyl residue of the trehalose unit. Thus, the glycolipid is decidedly amphipathic yet is clearly not membranous. This observation leads to speculation about the role of these novel lipooligosaccharides in contributing to the outer segment of the hydrophobic barrier of the cell wall of certain mycobacteria.

Chemical Phenomena↗
PubMed1987

Definition of the surface antigens of Mycobacterium malmoense and use in studying the etiology of a form of mycobacteriosis.

Mycobacterium malmoense is the latest of a roster of atypical mycobacteria implicated in pulmonary infections. Yet it lacks recognizable phenotypic features to allow its ready identification. Some 23 clinical isolates of M. malmoense were examined for homologous seroagglutination reactions and characteristic surface antigens. One group showed concordant agglutination interreactions and an identical spectrum of glycolipids and are regarded as M. malmoense sensu stricto. The glycolipids are of the newly found, trehalose-containing lipooligosaccharide class. De-O-acylation followed by high-pressure liquid chromatography revealed one major and several minor oligosaccharides. Partial acidic cleavage to release glycosidically linked trehalose, alpha-mannosidase digestion to demonstrate the presence of a non-reducing-end mannobiose, perdeuteriomethylation, partial acid hydrolysis, reduction, and O ethylation, combined with 1H nuclear magnetic resonance and electron impact and fast-atom bombardment mass spectrometry revealed the structure of the major oligosaccharide as alpha-D-Manp-(1----3) -alpha-D-Manp-(1----[2-alpha-L-Rhap-(1--]4--3)-alpha-L-Rh ap- (1----3)-alpha-D-Glcp-(1----1)-alpha-D-Glcp, in which two of the 2-alpha-L-Rhap residues are O methylated at C-3. (Man, mannose; Rha, rhamnose; Glc, glucose; p, pyranosyl). The structures of the minor oligosaccharides were also determined; they differ at the distal nonreducing end. The dominant oligosaccharide was acylated by octanoate, 2-methyleicosanoate, and 2,4-dimethylpentacosanoate to yield the major species-specific surface antigen of M. malmoense, which we regard as the most characteristic feature of the pathogen.

Agglutinins↗
PubMed1986

Structure of Plant Cell Walls : XVIII. An Analysis of the Extracellular Polysaccharides of Suspension-Cultured Sycamore Cells.

The water-soluble polysaccharides (SEPS) secreted into the medium by suspension-cultured sycamore cells were examined to determine whether the polysaccharides were the same as those present in the walls of sycamore cells. The SEPS were made more amenable to fractionation by treatment with a highly purified alpha-1,4-endopolygalacturonase (EPG). The EPG-treated SEPS were fractionated by anion-exchange and gelpermeation chromatography. The following polysaccharides were found: xyloglucan, arabinoxylan, at least two arabinogalactans, a rhamnogalacturonan-II-like polysaccharide, and a polygalacturonic acid-rich polysaccharide. The oligogalacturonide fragments expected from EPG-digested homogalacturonan were also identified. Evidence was obtained for the presence of a rhamnogalacturonan-I-like polysaccharide. All of the above polysaccharides have been isolated from or are believed to be present in sycamore cell walls. Furthermore, all of the noncellulosic polysaccharides known to be present in sycamore cell-walls appear to be present in the SEPS.

Journal Article↗
PubMed1985

Structure and function of plant cell wall polysaccharides.

Studies of the primary structures of polysaccharides of growing plant cell walls have shown that these structures are far more complex than was anticipated just a few years ago. This complexity can best be appreciated by considering xyloglucan, a hemicellulose present in the cell wall of both monocots and dicots, and rhamnogalacturonan II (RG-II) and rhamnogalacturonan I (RG-I), two structurally unrelated pectic polysaccharides. This realization led us to postulate that cell wall polysaccharides have functions beyond determining the size, shape and strength of plants. Some years ago we demonstrated that oligosaccharide fragments of a branched beta-linked glucan of fungal cell walls can elicit the production of phytoalexins (antibiotics) in plants by inducing the formation of the enzymes responsible for synthesis of the phytoalexins. It has now been ascertained and confirmed by synthesis that the elicitor activity resides in a very specific hepta-beta-D-glucoside. The heptaglucoside has been shown to elicit phytoalexins by activating the expression of specific genes, that is, by causing the synthesis of the mRNAs that encode the enzymes that synthesize phytoalexins. In other words, complex carbohydrates can be regulatory molecules. Further experiments established that oligosaccharide fragments of polysaccharides, produced by acid or base hydrolysis or by enzymolysis of primary cell walls of plants, also evoked defence responses in plants. Subsequently, we learned that defined fragments of polysaccharides, released from covalent attachment within plant cell walls, can function as regulators of various physiological processes such as morphogenesis, rate of cell growth and time of flowering and rooting, in addition to activating mechanisms for resisting potential pathogens. Examples of plant oligosaccharides with regulatory properties (called oligosaccharins) will be described.

Cell Survival↗