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

Hemadsorbing revertants were isolated from spontaneous hemadsorption-negative, avirulent mutants of Mycoplasma pneumoniae. The revertants simultaneously reacquired specific proteins absent in their homologous mutants, along with neuraminidase-sensitive adherence to the respiratory epithelium and virulence. Peptide mapping and immunological analysis indicated no precursor-product relationships among certain of these proteins.
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PMID:Reacquisition of specific proteins confers virulence in Mycoplasma pneumoniae. 640 61

A selective enrichment technique was used to isolate a hemadsorption-positive revertant of a hemadsorption-negative mutant strain of Mycoplasma pneumoniae. This hemadsorption-positive revertant was shown to have simultaneously regained both the ability to attach to neuraminidase-sensitive receptors on the tracheal ring respiratory epithelium in vitro and the ability to synthesize three virulent-strain-specific proteins which were not synthesized by the hemadsorption-negative mutant. Despite the persistence of the revertant in hamster lung tissue for 9 to 12 weeks postinfection, no cytopathology was observed. Intranasal inoculation of the revertant provided limited protection against a challenge dose of virulent M. pneumoniae.
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PMID:Hemadsorption and virulence are separable properties of Mycoplasma pneumoniae. 640 62

Mycoplasma pneumoniae and M. gallisepticum possess binding sites of protein nature which mediate attachment to neuraminidase-sensitive regions on both respiratory epithelium and red blood cells. The binding sites of these organisms are similar though not identical. Several approaches were applied for the isolation of the binding sites. Of these, the use of affinity chromatography yield the least complex protein fraction. We have recently been using sialoglycopeptides as the ligands in affinity chromatography. The availability of monoclonal antibodies which inhibit the attachment of M. pneumoniae to host cells should provide a very specific tool for the isolation of the attachment moiety. It should be mentioned that not all mycoplasmas adhere to host cells via sialic acid specific receptors, and other approaches should be developed to study these mycoplasmas' attachment moieties.
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PMID:Purification of attachment moiety: a review. 643 78

A new method for the in vitro culture of entire, intact tracheas from adult guinea pigs is described. Matrix-embed/perfusion (MEP) culture is based on an immobilization of the tissue in nutrient agar The tubular piece of agar-embedded organ was contained in a special perfusion block with two wells for liquid medium at either end. When incubated on a rocker platform, liquid medium flows through the trachea and supplies oxygen an nutrients. In this configuration, tracheas maintain near-normal metabolism (ATP content and dehydrogenase activity), structure (as determined by light and electron microscopy), and function (ciliary motion). Tissues could be maintained in vitro in a normal for at least 4 wk, with reduced ciliary motion and cell metabolism detectable for at least 6 wk. Agar-embedded tissues from the MEP cultures were nearly identical to those cultivated with standard tracheal ring explant techniques. Tracheas in the MEP cultures were infected with Mycoplasma pneumoniae. Attachment was neuraminidase-sensitive. Mycoplasma attachment was lowest on the epithelium along the dorsal ridge, but was uniform along the length of the trachea. Ciliostasis and cytonecrosis induced by M. pneumoniae was dose dependent. The matrix-embed/perfuse technique appears to have considerable potential for several types of in vitro studies on trachea or other tubular organs.
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PMID:Mycoplasma pneumoniae infection of intact guinea pig tracheas cultured in a unique matrix-embed/perfusion system. 679 99

Interaction between Acholeplasma laidlawii cells labelled with oleic acid and mouse spleen lymphocytes depended on the time of incubation, on the temperature and on the quantitative ratio between both cells. Uncouplers and EDTA did not influence the intensity of attachment. The resistance of binding to cytochalasin B amd glutaraldehyde as well as localization of A. laidlawii antigens on the lymphocyte surface and experiments with [14C] uridine-labelled mycoplasmas are an evidence against the participation of pinocytosis in this interaction. Prolonged attachment of intact A. laidlawii to washed lymphocytes can be excluded on the basis of an extremely low amount of CFU recovered from disrupted lymphocytes as well as by experiments with uridine-labelled A laidlawii. Specific receptors didn't take part in the binding, because proteolytic enzymes and neuraminidase treatment proved to be nonefficient. Increased binding of lymphocytes with liposomes prepared from mycoplasma lipids as well as the transfer of cholesterol from lymphocyte membrane to mycoplasma membrane demonstrate the participation of membrane lipids in this binding. It should also be mentioned that after the attachment between both cell types and fusion of A. laidlawii cells with lymphocytes takes place. The transfer of unsaturated fatty acids from mycoplasmas into lymphocyte membrane as well as lymphocyte membrane cholesterol into mycoplasma membranes are the consequence of fusion between both cells. The experiments with uncharged hydrophobic fluorescent probe 4-DMC are the direct proof of fusion and mutual exchange of lipid membrane components.
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PMID:Interactions of Acholeplasma laidlawii cells with mouse spleen lymphocytes. 679 54

Twenty-two mutants of Mycoplasma pneumoniae spontaneously deficient in hemadsorption were isolated. Examination of mutant protein profiles by one- and two-dimensional polyacrylamide gel electrophoresis permitted the grouping of these mutants into four classes. The largest class of mutants was deficient in four high-molecular-weight proteins (215,000, 210,000, 190,000, and 140,000). A second class of mutants lacked three proteins previously designated A, B, and C (72,000, 85,000, and 37,000, respectively). A single mutant, in addition to lacking proteins A, B, and C, was missing a fourth protein of 165,000 molecular weight. The remaining mutants exhibited protein profiles apparently identical to that of the wild-type strain. All mutant strains attached to the respiratory epithelium of hamster tracheal rings in vitro at reduced levels; however, mutants lacking proteins A, B, and C recognized only neuraminidase-insensitive receptors. None of the mutants tested produced detectable pneumonia in intranasally inoculated hamsters, although one mutant class demonstrated low-level survival in vivo.
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PMID:Identification of Mycoplasma pneumoniae proteins associated with hemadsorption and virulence. 680 61

Mycoplasma pneumoniae must attach to respiratory tract cells to cause primary atypical pneumoniae. The attachment process involves a receptor site on the external membrane surface of the host cell and a specialized attachment tip on the mycoplasmal cells. Attachment to lung fibroblasts and ciliated tracheal explants is time dependent, with maxima reached in 45-90 min at 37 C. Attachment to ciliated cells is slower, apparently because of continuous ciliary motion. Normally, less than 10% of available mycoplasmas become cell associated in vitro, perhaps because the pathogen must be in a particular growth phase or because only a small fraction of the M. pneumoniae population has complete or effective attachment tips. Mycoplasmas that attach to host cells normally have the constricted attachment tip oriented toward the host cell surface. Mycoplasmas are oriented vertically in cultures of densely ciliated cells, but can lie horizontally alone--and in close apposition to--cell membranes of sparsely ciliated or nonciliated cells. The site to which M. pneumoniae attaches, a sialoglycoprotein, is readily inactivated by neuraminidase, partially sensitive to pronase, and resistant to trypsin. Purified glycoprotein extracts bind to M. pneumoniae.
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PMID:A review of the morphological and biochemical features of the attachment process in infections with Mycoplasma pneumoniae. 681 1

Mycoplasmas are typical surface parasites colonizing the mucous membranes of animals and man. Efficient adherence mechanisms are therefore a prerequisite for survival and, in some species, for pathogenicity. The lack of a rigid cell wall enables the mycoplasmas, in contrast to bacterial mechanisms, to actively rearrange their surface structure in a vertical or horizontal direction. The energy requirement for attachment of M. pneumoniae in inert surfaces strongly suggests such a mechanism, although no supporting morphological data are yet available. There seem to exist different kinds of adherence mechanisms depending on the species of mycoplasma and the host involved. The receptors of sheep erythrocytes for M. pneumoniae, M. gallisepticum and M. dispar are neuraminidase-sensitive, whereas those for M. hominis and M. salivarium are not, but are protease-sensitive. On the other hand the receptors of rabbit red blood cells for M. pneumoniae and M. dispar are neuraminidase-resistant. The binding sites on the mycoplasma surface too differ in some properties. Data on M. pneumoniae suggest a protein as major constituent of the binding mechanism. The results of all studies are to some extent also dependent on the method used to examine adherence. Most work was done with either hemagglutination and hemadsorption or with attachment to cells and organ cultures. A special experimental system is provided by the adherence of some species to glass or plastic surfaces. On this model the role of energy metabolism could be studied in more detail. Further strategy of research must include biochemical methods as well as morphological and immunological approaches.
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PMID:Adherence of mycoplasmas to cells and inert surfaces: phenomena, experimental models and possible mechanisms. 728 16

A microtiter plate adherence assay for Mycoplasma hyopneumoniae was established by use of purified swine tracheal cilia which contained receptors for the mycoplasmas. M. hyopneumoniae bound specifically to plates coated with solubilized cilia. The binding was dependent on both the concentration of cilia and the number of mycoplasmas. Dextran sulfate, heparin, chondroitin sulfate, laminin, mucin, and fucoidan significantly inhibited the binding of the mycoplasmas. The six inhibitors also disrupted the adherence of the mycoplasmas to intact ciliated cells. Preincubation with either mycoplasmas or cilia indicated that heparin, mucin, fucoidan, and chondroitin sulfate interacted with the adhesive molecules on the surface of the mycoplasmas, while laminin blocked the receptors in cilia. The basis for the inhibition induced by dextran sulfate was unknown. Treatment of cilia with neuraminidase appeared to promote adherence of the mycoplasmas, whereas treatment of cilia with sodium metaperiodate decreased binding. These results indicate that receptors for M. hyopneumoniae in the ciliated epithelium of the respiratory tract of pigs are glycoconjugate in nature.
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PMID:Microtiter plate adherence assay and receptor analogs for Mycoplasma hyopneumoniae. 816 22

Among the wall-less mycoplasmas only a few species have been identified with a capsule at their cell surface. Mycoplasma penetrans is a recently identified mycoplasma with unique morphology, isolated from HIV-infected patients. Using transmission electron microscopy, it was found that M. penetrans is surrounded by capsular material 11 nm (strain GTU-54-6A1) to 30 nm (strain HF-2) thick, which can be stained with ruthenium red and labelled with cationized ferritin. The polysaccharide composition of this capsule was indicated by its staining with periodic acid-thiocarbohydrazide silver proteinate and the abolition of ruthenium red staining of the cell surface by neuraminidase treatment. In addition, proteinase K treatment of the M. penetrans cells resulted in removal of the capsule, suggesting that polypeptides may contribute in anchoring it to the membrane or in its stability. Two different types of glycosylated material were detected in mycoplasma extracts by SDS-PAGE and periodic acid-Schiff staining. The first component was a high-molecular-mass material, which was heat- and proteinase-K-labile and which probably constitutes the capsular polymer. The other component was a low-molecular-mass glycolipid fraction, which was proteinase-K-, heat- and EDTA-resistant. The identification of a capsule at the M. penetrans cell surface is of particular interest for a mycoplasma which has been shown to adhere to various host cells and to penetrate into their intracellular compartments. The capsule may have significance in the pathogenesis of disease associated with infection by this organism.
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PMID:Identification of two glycosylated components of Mycoplasma penetrans: a surface-exposed capsular polysaccharide and a glycolipid fraction. 961 99


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