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Query: UMLS:C0026936 (Mycoplasma)
 14,761 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pathogenic mycoplasmas adhere to and colonize the epithelial lining of the respiratory and genital tracts of infected animals. An experimental system suitable for the quantitative study of mycoplasma adherence has been developed by us. The system consists of human erythrocytes (RBC) and the avian pathogen Mycoplasma gallisepticum, in which membrane lipids were labeled. The amount of mycoplasma cells attached to the RBC, which was determined according to radioactivity measurements, decreased on increasing the pH or ionic strength of the attachment mixture. Attachment followed first-order kinetics and depended on temperature. The mycoplasma cell population remaining in the supernatant fluid after exposure to RBC showed a much poorer ability to attach to RBC during a second attachment test, indicating an unequal distribution of binding sites among cells within a given population. The gradual removal of sialic acid residues from the RBC by neuraminidase was accompanied by a decrease in mycoplasma attachment. Isolated glycophorin, the RBC membrane glycoprotein carrying almost all the sialic acid moieties of the RBC, inhibited M. gallisepticum attachment, whereas asialoglycophorin and sialic acid itself were very poor inhibitors of attachment. Only part of the (125)I-labeled glycophorin bound to mycoplasmas could be removed by neuraminidase or by exchange with unlabeled glycophorin. It is suggested that glycophorin, representing the isolated major RBC receptor for M. gallisepticum, binds to the mycoplasmas both specifically, through its sialic acid moieties, and nonspecifically, through its exposed hydrophobic polypeptide moiety.
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PMID:Adherence of Mycoplasma gallisepticum to human erythrocytes. 2 7

The human pathogen Mycoplasma pneumoniae adheres to a variety of cells, including erythrocytes. A hemadsorption technique was developed to quantitate adherence by photometric measurement of lysates of erythrocytes that attached to sheets of M. pneumoniae grown in cups of Linbro plates. Attachment of sheep erythrocytes (SE) increased with higher ionic strength, was unaffected by minor pH variations (6 to 9), and was blocked by anti-M. pneumoniae antiserum, but was not inhibited by a variety of sugars, amino acids, and bovine serum albumin. The reaction was time and temperature dependent. The temperature curve showed peaks at 14 and 28 degrees C with untreated SE but only one peak at about 38 degrees C with glutaraldehyde-treated SE. The temperature dependence indicated involvement of either metabolic or membrane activities in the binding process. Trypsin treatment of the M. pneumoniae sheet abolished adherence of SE but was only partially effective with human erythrocytes and noneffective with rabbit erythrocytes. The binding capacity of the mycoplasma cells for SE was restored by incubation in growth medium for 3 to 4 h; this restoration was inhibited by 10 mug of chloramphenicol per ml. Neuraminidase treatment of SE removed their attachment capacity but had no effect on attachment of rabbit erythrocytes and only a slight effect on attachment of human erythrocytes. Pretreatment of M. pneumoniae with neuraminic acid partially blocked the adherence of SE, whereas rabbit erythrocyte attachment was not affected. Attached SE could be detached by trypsin, but not by neuraminidase. For human and rabbit erythrocytes, the results suggest binding mechanisms other than the interaction between neuraminidase-sensitive receptors and protein-containing binding sites shown for SE.
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PMID:Adherence of erythrocytes to Mycoplasma pneumoniae. 3 34

The interaction of pathogenic Mycoplasma pneumoniae and host cells was studied in cell cultures of MRC-5 human lung fibroblasts. A comparison of results obtained with fibroblasts in a monolayer format and with hamster tracheal explant cultures indicated that the former can bind significantly larger numbers of mycoplasmas. In addition, the attachment was 96% specific, that is, mediated through a neuraminidase-sensitive receptor on the host cell. Uptake of mycoplasmas was directly related to the number of mycoplasma cells present in the inoculum, and attachment was virtually complete within a 30-min period at 37 degrees C. High doses of M. pneumoniae induced a marked cytopathic effect, whereas doses of less than or equal to 10(6) colony-forming units per ml produced grossly observable cell damage that was moderate and variable. Transmission electron microscopy studies indicated that attachment of M. pneumoniae to the surface of lung fibroblasts occurred with the specialized terminal structure or binding site oriented closest to the epithelial cell surface. The filamentous mycoplasma cells were spatially arranged in several configurations and were not limited to a vertical orientation. The advantages and disadvantages of human lung fibroblast monolayer cultures, in reference to other in vitro models are discussed. A new mycoplasma agar medium (G-200 agar) with a defined tissue culture base and 10% horse serum is also described.
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PMID:Interaction of Mycoplasma pneumoniae with human lung fibroblasts: characterization of the in vitro model. 11 48

The biochemical nature of the neuraminidase-sensitive Mycoplasma pneumoniae receptor site on human lung fibroblast cells was studied. Purified, mixed sialoglycolipid (ganglioside) preparations from human and bovine tissues did not bind to M. pneumoniae organisms and block their subsequent attachment to fibroblasts. Fibroblasts incubated for 24 h in sialoglycolipid solutions to increase the ganglioside content of their membranes did not show increased pathogen attachment when later incubated with mycoplasmas. HeLa cells grown in the presence of sodium butyrate to increase GM3 ganglioside levels likewise did not have significantly increased uptake of M. pneumoniae organisms. Treatment of fibroblasts with enzymes indicated that the mycoplasma receptor site is trypsin and papain resistant but Pronase sensitive. Pronase digests of fibroblast membranes contained a product(s) which combined with M. pneumoniae cellls and cosedimented with them during centrifugation. Glycoproteins, purified from fibroblast membranes by a lithium diiodosalicylate solubilization technique, similarly bound to M. pneumoniae organisms. Collectively, these data suggest that the major component of the M. pneumoniae receptor site is a sialoglycoprotein with little or no lipid.
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PMID:Interaction of Mycoplasma pneumoniae with human lung fibroblasts: role of receptor sites. 11 49

Mycoplasma synoviae was tested for its ability to grow and induce cytopathogenic changes in chicken embryo cell cultures. M. synoviae grew to high titers by day 5 in the presence of chick cells, but showed no growth in the tissue culture medium alone even though it was enriched with nicotinamide adenine dinucleotide and swine serum. Infected chick cell cultures showed a progressive cytoplasmic degeneration on successive days of examination. Early changes involved cytoplasmic granularity and mild vacuolation. On the last day of examination the cytoplasm of most cells was completely degenerated and some showed nuclear degeneration. M. synoviae was shown to be cytophilic for the chick cell membranes where the mycoplasmas reproduced and formed microcolonies which, on successive days, increased in size. The attachment site on the chick cell membrane was shown to be neuraminidase sensitive.
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PMID:Growth and cytopathology of Mycoplasma synoviae in chicken embryo cell cultures. 16 27

The attachment of radioisotope-labeled Mycoplasma pneumoniae to hamster tracheal rings in organ culture was examined by radioautography and liquid scintillation counting. Radioautographs of individual rings exposed for 8 h to (3H) thymidine-labeled virulent M. pneumoniae revealed a dense extracellular collection of emulsion grains along the luminal surface of epithelial cells. Similar exposure of rings to isotope-labeled avirulent M. pneumoniae resulted in no accumulation of emulsion grains. The numbers of attached virulent mycoplasmas, as measured by liquid scintillation counting of infected rings, were found to increase in a nearly linear fashion over an 8-h incubation period. Viability of the mycoplasmas and metabolic integrity of the tracheal rings were important for optimal attachment. Pretreatment of rings with neuraminidase or sodium periodate significantly impaired orgainism adherence. These data suggest a specificity of interation between virulent M. pneumoniae and tracheal epithelial cells that can be further examined through the use of isotopically labeled mycoplasmas.
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PMID:Attachment of Mycoplasma pneumoniae to respiratory epithelium. 17

An organ culture system for hamster trachea was developed for maintenance of the ciliated respiratory epithelium during periods of extended cultivation (i.e., greater than 20 days). Evaluation of five serum types showed that horse serum and fetal calf serum were best for the maintenance of epithelial ciliary activity and morphology. Rings that were opened on one side ("split rings") had the best maintenance of the ciliated epithelium as judged by the retention of ciliary activity and normal histological appearance after 3 to 4 weeks in culture. The in vitro induction of squamous metaplasia was achieved by cultivating explants in Waymouth MAB 87/3 (vitamin A-free) medium, without serum. This system allowed a direct comparison of the effects of Mycoplasma pneumoniae infection in two epithelial types, ciliated pseudostratified columnar and keratinizing squamous. Attachment of 14C-labeled mycoplasmas was more than twofold greater in the normal epithelium. Pretreatment of explants with neuraminidase decreased attachment for both squamous and pseudostratified epithelial surfaces to a similar basal level. Recovery of viable organisms from infected tissue of both epithelial types indicated that the organism titer remained essentially constant during the infection period, but was significantly higher for the pseudostratified ciliated epithelium. These results suggest that specific receptor sites for M. pneumoniae are markedly reduced by the induction of squamous metaplasia and, hence, appear to be specific for the normal respiratory surface containing goblet cells and pseudostratified, ciliated epithelial cells.
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PMID:Effect of squamous metaplasia on infection of hamster trachea organ cultures with Mycoplasma pneumoniae. 55 58

Hamster trachea organ cultures were exposed to isolated membranes of Mycoplasma pneumoniae, PI 1428. Attachment, monitored by the uptake of tritiated membranes, was relatively insensitive to neuraminidase pretreatment, unlike the attachment of viable cells. Membrane attachment was optimal when explants were incubated with 50 to 100 micrograms of membrane protein per ml in minimal essential medium broth while gently being rotated (1 rpm) in a roller apparatus for 90 to 120 min at 37 degrees C. Saturation of the receptor sites with viable cells failed to inhibit subsequent membrane attachment. Induction of squamous metaplasia by extended cultivation of tracheal explants in a vitamin A-free medium reduced the content of ciliated cells without significantly affecting total cell viability, but did not alter the attachment of M. pneumoniae membranes. Collectively, the data indicate that the mechanism of attachment of M. pneumoniae membranes to respiratory epithelium is distinct from the receptor site-mediated attachment of M. pneumoniae cells.
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PMID:Differences in the attachment of Mycoplasma pneumoniae cells and membranes to tracheal epithelium. 56 Oct 31

Hamster respiratory epithelial cells were cultured in a monolayer format, and 20% of the cells were ciliated. Mycoplasma pneumoniae attached to the epithelial cells in a neuraminidase-specific fashion and induced ciliostasis and cytonecrosis.
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PMID:Ciliated respiratory epithelial monolayers: new model for Mycoplasma pneumoniae infection. 71 20

The activities of alpha- and beta-glucosidase, beta-galactosidase and beta-N acetylglucosaminidase were assessed at acidic pH by fluorimetry using the appropriate 4-methylumbelliferyl substrate in four Mycoplasma species (M. pneumoniae, M. gallisepticum, M. hominis and M. capricolum) and in Acholeplasma laidlawii. The glycosidase activities were in a low range (0.1-4.2 nmole per h per mg protein) with the exception of higher activities of beta-N-acetylglucosaminidase in A. laidlawii. The enzyme levels of a virulent and a nonvirulent strain of M. pneumoniae were comparable. Despite the very sensitive assay, neuraminidase activity was not detected in M. pneumoniae and M. gallisepticum. No induction of alpha-glucosidase could be demonstrated for M. pneumoniae or A. laidlawii. At least part of the glycosidase activities was localized in the membrane fraction of all mycoplasmas studied. This may support the hypothesis that pathogenic mycoplasmas, being membrane parasites, may modify, by their glycosidases, some host cell glycoconjugates. However, our study did not distinguish the pathogenic mycoplasmas to possess a characteristic glycosidase profile.
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PMID:Glycosidase activities of mycoplasmas. 211 90


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