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

Mycoplasma pulmonis is a murine pathogen that causes chronic respiratory disease in laboratory rats and mice. Several examples of high-frequency phenotypic switching have been reported for M. pulmonis, the molecular basis of which is unknown. We report here that during growth the M. pulmonis chromosome undergoes DNA rearrangements at a high frequency. Some of the rearrangements we examined correlated with changes in the susceptibility of the cells to mycoplasma virus P1, an example of phenotypic switching involving changes in surface antigen structure. Other rearrangements, unrelated to phenotypic switching, involved a DNA element present in the chromosome in multiple copies. The high level of DNA recombination that occurred in M. pulmonis indicates that this may be one of the most variable genomes studied to date. High levels of DNA recombination may contribute to the unusually high rate of evolution that mycoplasmas are thought to be undergoing. Understanding the molecular basis for this phenomenon may provide an insight into the chronic nature of many mycoplasmal infections.
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PMID:High-frequency rearrangements in the chromosome of Mycoplasma pulmonis correlate with phenotypic switching. 135 Mar 16

A previously defined immunoglobulin M(kappa) monoclonal antibody reacting with a surface epitope of Mycoplasma hyorhinis is shown in this report to mediate specific, complement-dependent mycoplasmacidal activity. Immunoblot analysis of mycoplasma components and their tryptic cleavage products showed that the epitope recognized was present on a protein with an apparent molecular weight of 23,000 (p23) and on a limit tryptic fragment of this protein with an apparent molecular weight of 18,000 (p18). Both p23 and p18 are shown by Triton X-114 phase fractionation to partition efficiently into the hydrophobic detergent phase. Other antigens bearing epitopes not expressed at the cell surface were present among the numerous hydrophilic proteins found in the aqueous phase. The external orientation and membrane association of the p23 antigen were further established by demonstrating that trypsin treatment of intact mycoplasmas generated the antigenic p18 fragment, which remained tightly associated with the organism. These results localize an epitope responsible for antibody-mediated mycoplasma killing onto a specific, surface-exposed region of an integral membrane protein of this organism. Since the monoclonal antibody used in this study does not bind to the surface of all strains of M. hyorhinis, the epitope identified also defines a structural marker of antigenic surface variation within this species, a feature previously observed during serological classification of the organism. Analysis of the antigenic and structural features of the p23 surface antigen may therefore be useful in establishing mechanisms of surface antigen variation among integral membrane proteins of mycoplasmas that could dictate important antigenic characteristics recognized during chronic disease caused by these agents.
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PMID:Triton X-114 phase fractionation of an integral membrane surface protein mediating monoclonal antibody killing of Mycoplasma hyorhinis. 243 31

The biochemical and serological properties of 21 strains of Actinobacillus pleuropneumoniae biotype 2 isolated from haemorrhagic necrotic pleuropneumonia of swine were examined. For serologic typing, the indirect haemagglutination (IHA) and the double gel-diffusion tests were used. On the basis of their soluble surface antigens, our A. pleuropneumoniae biotype 2 isolates could be assigned to two proposed serotypes. Serotype 1 comprised 11 strains and serotype 2 comprised 10 strains. All strains contained two surface antigen components. In the strains belonging to serotype 1, one of the antigens was identical with the serotype-specific antigen of Pasteurella haemolytica T4. Both antigens of serotype 2 strains proved to be type-specific. Four strains received from Switzerland, including the holotype strain of A. pleuropneumoniae biotype 2, and three strains isolated from swine in the G.D.R. belonged to serotype 2. Both the double gel diffusion and the IHA tests detected a 2-way cross-reaction between biotype 1, serotype 2 and biotype 2, serotype 2 strains of A. pleuropneumoniae, which could be eliminated using cross-absorbed sera.
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PMID:Biochemical and serological properties of Actinobacillus pleuropneumoniae biotype 2 strains isolated from swine. 250 35

Heterogeneity in colony size of the murine pathogen Mycoplasma pulmonis was examined. Subcloning experiments showed that colony size variation resulted from high-frequency genetic changes. About 3% of the colonies from any given subclone were variants, with as much as a fourfold change in colony diameter. When the variants were propagated in liquid broth, their doubling times in logarithmic growth phase reflected the colony sizes obtained on agar. Colony size variation correlated with changes in the electrophoretic properties of the V-1 surface antigen.
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PMID:High-frequency variation in Mycoplasma pulmonis colony size. 276

A number of viruses have been implicated as being the cause of various forms of myositis, including acute transient myositis, chronic polymyositis, and dermatomyositis. However, the cause of juvenile dermatomyositis (JDM) has remained elusive. Our study of serum samples taken within 4 months of the onset of disease in 12 children with JDM showed that 83% had detectable titers of complement-fixing (CF) antibody to 1 or more coxsackie B viral antigens. Detectable titers were found in only 25% of age-, sex-, and date-matched control sera taken from 24 patients with juvenile rheumatoid arthritis (JRA), and in 25% of serum samples taken from 2,192 "normal" children who had been hospitalized because of viral syndromes. Titers of CF antibody to coxsackie B1, B2, and B4 were positive in 58%, 50%, and 58%, respectively, of the JDM patients. In matched JRA controls, the respective values were 8%, 13%, and 8%. There were no significant antiviral titers and no significant differences in the results of tests for 13 other viral CF antigens, hepatitis B surface antigen, and Mycoplasma pneumoniae CF antigen in the JDM patient sera compared with the JRA patient sera. When titers of neutralizing antibody were determined, 58%, 58%, and 67% of the JDM patients were positive for coxsackie B2, B4, and B5, respectively, whereas 16%, 26%, and 21%, respectively, of the JRA controls were positive for the 3 antigens. These data suggest that the host response to coxsackie B virus might be related to the pathophysiology of JDM.
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PMID:Prevalence of Coxsackie B virus antibodies in patients with juvenile dermatomyositis. 302 59

Surface structures of the genital mycoplasmas Ureaplasma urealyticum and Mycoplasma hominis that are important in the human immune response and pathogenesis of disease are relatively poorly defined. In this study, an unusual antigen complex of U. urealyticum consisting of multiple bands forming a "ladder" pattern after electrophoretic separation was noted. It is similar to the variable V-1 surface antigen of Mycoplasma pulmonis. Data on U. urealyticum are only preliminary, but the ureaplasma antigen, if it proves to be analogous to V-1, may provide the antigenic determinants for distinguishing among serovars or serogroups and correlating them with pathogenicity. Surface proteins of M. hominis were identified with use of 125I surface labeling, [35S]methionine metabolic labeling, and immunoadsorption of rabbit antiserum. Comparison of M. hominis reference strains PG-21 and 4195 showed little homology between surface proteins, although with metabolic labeling they appeared essentially identical. Immunoblotting with patients' sera, using PG-21 as antigen, showed that most reactions were directed to surface proteins and that a 102K antigen (MH1) was recognized by 94% of the sera. MH1 was one of the few surface proteins of PG-21 that appeared to have counterparts in the other six reference strains, making MH1 a prime candidate for reliable and specific detection of M. hominis infection.
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PMID:Protein antigens of genital mycoplasmas. 305 6

Sera from rats convalescing from infection with Mycoplasma arthritidis were tested for their ability to react with M. arthritidis membrane antigens by immunoblotting and radioimmunoprecipitation. The absence of metabolism-inhibition (MI) antibody activity in these sera suggested that rats might fail to recognize those membrane antigens involved in eliciting MI antibodies therefore rabbit antisera, which are strongly MI positive for M. arthritidis, were used for comparison. Antigenic recognition patterns of M. arthritidis surface and membrane antigens were not identical for rats and rabbits. The most striking and reproducible difference was the failure of rats to produce IgG antibodies against a surface antigen migrating in the 47,000-50,000 molecular weight range on SDS-polyacrylamide gels. However, rats recognized at least 2 antigens which we had previously shown to be "MI antigens", therefore the inability to express MI antibodies probably cannot be explained by their inability to recognize M. arthritidis "MI antigens".
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PMID:Recognition of Mycoplasma arthritidis membrane antigens by rats and rabbits: comparison by immunoblotting and radioimmunoprecipitation. 326 51

Monoclonal and monospecific antibodies were used to characterize a major Mycoplasma pulmonis surface antigen complex, V-1. Heterogeneity of V-1 was detected among strains and a high frequency of variation was detected within subclones of single strains. Analysis of 18 different strains showed that no two displayed identical electrophoretic immunoblot patterns for V-1. Analysis of 50 filter clones from an individual strain (not previously filter cloned) revealed at least 10 different V-1 patterns. The two most frequently occurring patterns were expressed by 36% and 24%, respectively, of the total population. Serial subcloning (four separate series) of several of these original clones showed that the average rate of V-1 variation was 2 x 10(-3) per cell per generation. Immunoblots with different anti-V-1 monoclonal antibodies demonstrated that there were both structurally and antigenically different forms of this antigen. Also, two-dimensional polyacrylamide gel analyses showed that different forms of V-1 could vary in charge. This potential for variability in a major surface antigen of mycoplasmas could have important implications as to how the organism interacts with its host.
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PMID:Heterogeneity among strains and a high rate of variation within strains of a major surface antigen of Mycoplasma pulmonis. 328 9

The adsorption of mycoplasma virus P1, a virus which infects some strains of Mycoplasma pulmonis, to host cells was examined. Mutants of M. pulmonis to which P1 virus did not adsorb were isolated. Proteins from the mutants and from wild-type cells were compared by two-dimensional polyacrylamide gel electrophoresis, and the only observed difference was in the surface antigen V-1. The electrophoretic properties of V-1 also correlated with the host range of the virus. These data strongly suggest that the V-1 antigen affects adsorption of P1 virus to host cells.
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PMID:Adsorption of mycoplasma virus P1 to host cells. 341 Aug 31

We have established a new human myeloma cell line from the pleural effusion of a patient with an IgA lambda myeloma, using special tissue culture conditions and selection procedures to prevent the outgrowth of contaminating Epstein-Barr virus (EBV)-carrying normal B-lymphoblastoid cells present in the explant. The myeloma cell line, U-2030, is aneuploid and EBNA-negative and has morphological features, reactivity with cytochemical markers and cell-surface antigen expression typical of plasmablasts. The cell line thus appears to be representative of the malignant clone in vivo. However, functionally the line is a non-Ig-producer and must therefore be derived from a non-secretory variant cell present within the highly aneuploid myeloma cell clone in vivo. The U-2030 differs from previously established human myeloma cell lines in that it has a comparatively high growth rate, is clonable and can be made HAT-sensitive relatively easily. This, together with the facts that it is a non-Ig-producer and mycoplasma-free, suggests that the 6-thioguanine-resistant, HAT-sensitive subline, U-2030 TG, derived from this cell line may be used as a malignant fusion partner for the production of human-human hybridomas. An EBV-carrying lymphoblastoid cell line (U-2031) was also established. This line was diploid and had all the phenotypic properties of lymphoblastoid lines established from normal individuals.
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PMID:Establishment of a new human myeloma cell line (U-2030) and selection of a hat-sensitive subline. 358 53


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