Biotype and macromolecular profiles of cytotoxin-producing strains of Helicobacter pylori from antral gastric mucosa

Biotype, genome, protein and plasmid profile diversity amongst 40 epidemiologically unrelated strains of Helicobacter pylori was studied. Strains were API Zym biotypes II, III and IV but most (87%) were biotype II. Four subsets of strains were defined on a combination of motility (56% positive) and cytotoxin production (44% positive). A close association (P = 0.45) between these two features was observed for 69% of strains. Each strain of H. pylori had a unique DNA type defined by either HaeIII or HindIII total digest patterns and by ribopatterns, except for DNA of the rare strains not cut by these endonucleases. Strain diversity was confirmed by one-dimensional SDS-PAGE electrophoretic protein patterns. No consistent associations between cytotoxin activity and overall ribopattern or band subsets within a ribopattern were detected. Some strains (39%) contained a plasmid but the presence of plasmids was not consistently associated with either cytotoxin activity, biotype, motility or ribopattern. We conclude that the cytotoxin-producing strains of H. pylori were genomically as diverse as the non-cytotoxin producing strains.     

Analysis of the nucleotide sequence of the Mycoplasma hominis tuf gene and its flanking region

A gene from Mycoplasma hominis PG21 similar to the tuf gene encoding the elongation factor Tu (EF-Tu) of Escherichia coli was cloned and sequenced. The 1193-bp open reading frame flanked by a putative promoter and a potential stem-and-loop structure encoded a 44-kDa polypeptide. The tuf gene of M. hominis PG21 has the lowest G + C content seen in prokaryotes (38.2%). A gene (mhlmp1) encoding a variable surface exposed membrane protein (LMP1) was found downstream the 3' end of the tuf gene. It was found that the highly conserved tuf gene was linked to the highly variable mhlmp1 gene in 26 different M. hominis strains.     

Symmetrical distribution and rapid transbilayer movement of cholesterol in Mycoplasma gallisepticum membranes

The exchange of cholesterol between [¹⁴C]cholesterol-labeled Mycoplasma gallisepticum cells and an excess of sonicated egg phosphatidylcholine/cholesterol vesicles (molar ratio of 0.9) was measured. More than 90% of the radioactive cholesterol underwent transfer from intact cells to the vesicles. The kinetics of the transfer was biphasic. About 50% of the radioactive cholesterol was exchanged with a half-time of about 4 h. The residual was exchanged at a slower rate with a half-time of about 9 h at 37°C. Bovine serum albumin had a pronounced effect in enhancing both the fast and slow rates of cholesterol exchange, but did not affect the pool sizes significantly. The half-time for equilibration of the two pools in the presence of 2% albumin, calculated using a reversible two-pool method of analysis, was 6.2 h. The effect of albumin was also obtained with isolated membrane preparations and with cells treated with growth inhibitors, suggesting that this effect is independent of albumin preservation of cell viability. The rate enhancement of albumin was concentration dependent with maximal effects observed with 2%, where the rates of exchange of both the rapidly and slowly exchanging pools were twice as fast. The mechanism by which albumin may affect the exchange rates is discussed.     

Reproduction of,and ultrastructural changes induced by,Spiroplasma citri in sieve tube of citrus leaves

Summary Electron microscope examination of ultrathin sections of leaf veins of stubborn—affected citrus seedlings revealed three morphotypes ofSpiroplasma citri free in the cytoplasm of mature sieve elements. In addition to these, inclusions believed to beSpiroplasma citri, some in various stages of degeneration, were occasionally found inside spherical, ovoid, or angular membraneous structures (= packets) which occurred in sieve elements devoid of any recognizable organelles. These packets which varied in size from 1.0 to 1.8 m wide an 1.9 to 3.5 m long were bounded by unit membrane ca. 9 to 10 nm thick. Spiroplasmas and packets were apparently absent in sieve elements of leaf veins of healthy citrus seedlings. Three types of packets were recognized based on the size of spiroplasmas contained: type I packets contained large, intermediate, and small spiroplasmas, but small forms predominated; type II packets contained a mixture of large and intermediate forms, while type III packets contained essentially tightly—packed large forms. Results of the study suggested that the spiroplasma-containing packets are either definite reproductive structures peculiar toSpiroplasma citri or are sieve-tube cells in various stages of plasmolysis. Evidence is presented indicating that within a given packet small spiroplasmas were produced from large spiroplasmas by some process of cell constriction followed by fission, or by budding. Since these spiroplasma—containing packets were infrequently observed in infected tissues we suggest that cell division by budding, of by constriction followed by fission into unequal daughter cells may be the principal mode of reproduction inSpiroplasma citri.     

Effect of in vitro cultivation andMycoplasma pneumoniae infection on intracellular cyclic AMP levels in hamster tracheal organ cultures

Summary Exogenous cyclic AMP and dibutyryl cyclic AMP decreased the relative ciliary activity values of tracheal organ cultures. In contrast, theophylline and cholera toxin were not ciliostatic. The use of a radioimmunoassay for cyclic AMP indicated that all of the tested substances increased intracellular cyclic AMP levels to some extent (from 3-fold for cholera toxin to almost 40-fold for dibutyryl cyclic AMP). Physical inactivation of explants by either freeze-thaw or heat destroyed all ciliary activity and greatly decreased intracellular cyclic AMP levels. Cyclic AMP levels of explants remained relatively constant during in vitro cultivation. Three strains ofMycoplasma pneumoniae were found to contain extremely low amounts of cyclic AMP. Infection of tracheal explants produced a significant decrease in relative ciliary activity, but only a slight decline in organ-culture cyclic AMP levels. This study was supported in part by Grant AI 12559 from the National Institutes of Health. The supply of cholera toxin from Dr. R. A. Finkelstein is most appreciated as are the assistance and advice of J. A. Engelhardt and Y. D. B. Stahl.     

EPO工程细胞株支原体检测

支原体污染是细胞培养过程中最常见的问题之一,对细胞支原体的检测是细胞特性鉴定的重要方面。我们采用抗支原体单抗免疫荧光法和培养法(包括液体培养法和固体培养法)检测工程细胞支原体。单抗免疫荧光法检测结果表明:支原体阳性的细胞膜表面有明亮荧光,工程细胞EPO C_2细胞膜表面无荧光。支原体液体培养法结果显示:作为阳性对照的支原体由于在生长过程中产酸使培养液变黄,而加入EPOC_2株细胞悬液的样品管与阴性对照管相同,无颜色变化。固体培养法结果显示:在显微镜下观察,支原体阳性对照在固体培养基上呈荷包蛋样集落,而阴性对照及EPO C_2株细胞样品均无菌落生长。以上结果表明:受检的EPO C_2株细胞未被支原体污染。     

猪肺炎支原体感染诱导的固有免疫应答研究进展

猪肺炎支原体是引起猪支原体肺炎的病原。由于缺乏成熟的猪肺炎支原体感染动物模型,使得猪肺炎支原体相关的抗感染免疫研究进展较为缓慢。本文从猪肺炎支原体感染后的炎症反应、固有免疫系统对猪肺炎支原体的识别、固有免疫细胞的作用、补体系统、抗菌肽、自噬以及细胞凋亡7个方面进行综述,旨在阐明固有免疫系统各组分在猪肺炎支原体感染中发挥的作用的研究进展,并对今后猪肺炎支原体感染的固有免疫应答研究的重点方向进行展望。     

The effect of Mycoplasma arthritidis infection on the kinetics of colloidal carbon clearance in mice

Abstract The activity of phagocytes from A/J mice was estimated by the carbon clearance test following injection of Mycoplasma arthritidis . Phagocytic activity was significantly depressed 12 h post-infection ( P =0.001) and returned to normal values at 24 h. For animals examined 2 and 7 days post-infection, the overall phagocytic activity increased significantly ( P <10⁻⁴). Phagocytic activity gradually decreased and returned to that of the control group by the end of the fourth week. The relative weights of liver and spleen were significantly increased from the 2nd day post infection ( P =0.0028 and P =0.0014 respectively) and remained increased until the end of the experiment. The early depressive effect on phagocytic activity may be related to superantigen activity with the production of mediators such as macrophage deactivating factor. The later expansion of the macrophage population might bring about the stimulation of autoreactive clones of T and B cells and be responsible for the chronic arthritis that developed in the mycoplasma treated mice.     

Interactions of cultured rat synovial and ocular ciliary body cells with two strains of mycoplasma arthritidis

Summary Strains ofMycoplasma arthritidis differ in their ability to cause joint and ocular inflammations. Although the reasons for this difference are not fully understood, pathogenic myćoplasmas commonly require close associations with the cells they damage. Using³H-uridine labeled mycoplasma, we compared cellular interactions of in vitro cultivated rat synovial and ocular ciliary body epithelial cells with two American Type Culture Collection strains ofM. arthritidis shown to differ in their virulence. Radiolabeling assays gave evidence of á stronger retention capability on cultured cells by the more pathogenic strain, 14152. Scanning electron microscopy demonstrated cellular associations with the two strains of mycoplasma, with more of the 14152 adhering to both cell types. Examination by transmission electron microscopy showed evidence of contact between the more virulent 14152 strain and both cell types, but no similar evidence with the comparatively less virulent strain, 19611. The pathogenicity of different strains ofM. arthritidis may vary according to their ability to closely associate with specific target cells involved in the disease process. This work was supported by funding from the National Society for the Prevention of Blindness, Fight for Sight, Retinitis Pigmentosa International, grant EY05415 from the National Institutes of Health, Bethesda, MD, to Thirkill, and, in part, by an unrestricted grant from Research to Prevent Blindness.     

Identification of an isoschizomer of the HhaI DNA methyltransferase in Mycoplasma arthritidis

The genome of Mycoplasma arthritidis strain 158 has modified cytosine residues at AGCT sequences that render the DNA resistant to digestion with the AluI restriction endonuclease. The DNA methyltransferase responsible for the base modification has previously been designated MarI. From the complete genome sequence of M. arthritidis , we identify Marth_orf138 as a candidate marI gene. Marth_orf138 was cloned in Escherichia coli and its TGA codons converted to TGG. DNA isolated from E. coli cells expressing the modified Marth_orf138 gene was degraded by the AluI nuclease, indicating that Marth_orf138 does not code for MarI. However, the DNA from E. coli was found to have acquired resistance to the restriction endonuclease HhaI. Genomic DNA from M. arthritidis was also found to be resistant to HhaI (recognizes GCGC). The M. arthritidis isoschizomer of the HhaI DNA methyltransferase, coded by Marth_orf138, is designated MarII. Transformation of M. arthritidis was not significantly affected by modification of plasmid at HhaI sites, indicating that the mycoplasma lacks a restriction endonuclease that recognizes GCGC sites.