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S Razin

Publications and source records attributed to S Razin.

At least 19 recordsLinked to original sources
PubMed1999

Adherence of pathogenic mycoplasmas to host cells.

The significant genome compaction in mycoplasmas was made possible by adoption of a parasitic lifestyle. During their evolution and adaptation to a parasitic mode of life the mycoplasmas have developed various genetic systems enabling their attachment to host tissues as well as a highly plastic set of variable surface proteins. The generation of a versatile surface coat through high-frequency phase and size variation provides the organism with a useful tool for immune system avoidance, allowing the mycoplasmas to escape antibody attack, explaining why these minute organisms are such successful parasites.

Adhesins, Bacterial↗
PubMed1998

Molecular biology and pathogenicity of mycoplasmas.

The recent sequencing of the entire genomes of Mycoplasma genitalium and M. pneumoniae has attracted considerable attention to the molecular biology of mycoplasmas, the smallest self-replicating organisms. It appears that we are now much closer to the goal of defining, in molecular terms, the entire machinery of a self-replicating cell. Comparative genomics based on comparison of the genomic makeup of mycoplasmal genomes with those of other bacteria, has opened new ways of looking at the evolutionary history of the mycoplasmas. There is now solid genetic support for the hypothesis that mycoplasmas have evolved as a branch of gram-positive bacteria by a process of reductive evolution. During this process, the mycoplasmas lost considerable portions of their ancestors' chromosomes but retained the genes essential for life. Thus, the mycoplasmal genomes carry a high percentage of conserved genes, greatly facilitating gene annotation. The significant genome compaction that occurred in mycoplasmas was made possible by adopting a parasitic mode of life. The supply of nutrients from their hosts apparently enabled mycoplasmas to lose, during evolution, the genes for many assimilative processes. During their evolution and adaptation to a parasitic mode of life, the mycoplasmas have developed various genetic systems providing a highly plastic set of variable surface proteins to evade the host immune system. The uniqueness of the mycoplasmal systems is manifested by the presence of highly mutable modules combined with an ability to expand the antigenic repertoire by generating structural alternatives, all compressed into limited genomic sequences. In the absence of a cell wall and a periplasmic space, the majority of surface variable antigens in mycoplasmas are lipoproteins. Apart from providing specific antimycoplasmal defense, the host immune system is also involved in the development of pathogenic lesions and exacerbation of mycoplasma induced diseases. Mycoplasmas are able to stimulate as well as suppress lymphocytes in a nonspecific, polyclonal manner, both in vitro and in vivo. As well as to affecting various subsets of lymphocytes, mycoplasmas and mycoplasma-derived cell components modulate the activities of monocytes/macrophages and NK cells and trigger the production of a wide variety of up-regulating and down-regulating cytokines and chemokines. Mycoplasma-mediated secretion of proinflammatory cytokines, such as tumor necrosis factor alpha, interleukin-1 (IL-1), and IL-6, by macrophages and of up-regulating cytokines by mitogenically stimulated lymphocytes plays a major role in mycoplasma-induced immune system modulation and inflammatory responses.

Animals↗
PubMed1997

Comparative genomics of mycoplasmas.

The mycoplasmas are the smallest and simplest self-replicating organisms. The goal of defining in molecular terms the entire machinery of a living cell by using mycoplasmas as models was put forward by Harold Morowitz in 1984. The recent complete sequencing of the genomes of the human pathogens Mycoplasma genitalium and Mycoplasma pneumoniae brings us much closer to achieving this goal. The M. genitalium genome contains only 479 predicted protein coding sequences (genes) and that of M. pneumoniae 677, as compared with 1703 in Haemophilus influenzae and about 4000 in E. coli. Thus, M. genitalium is apparently the simplest organism capable of independent life with a minimal set of genes. The drastic economization in genetic information must have been associated with the parasitic mode of life of the mycoplasmas. During their reductive evolution from Gram-positive bacteria the mycoplasmas have lost the cell wall and many biosynthetic systems involved in synthesis of macromolecule building blocks provided by their host. Thus, the M. genitalium and M. pneumoniae genomes do not carry any gene involved in amino acid biosynthesis, and very few genes for vitamin, nucleic acid precursor and fatty acid biosynthesis. The mycoplasma genomes carry a minimal set of energy metabolism genes, being content with a restricted supply of ATP needed for their parasitic mode of life. Nevertheless, these minimal organisms carry the essential genes for DNA replication, transcription and translation, but even here gene saving is expressed by a minimal number of rRNA and tRNA genes. A genomic price had been paid to maintain parasitism, so that a significant number of mycoplasmal genes is devoted to adhesins, attachment organelles and variable membrane surface antigens directed towards evasion of the host immune system.

Animals↗
PubMed1995

Use of ECFMG certifying examinations for national comparisons: performance of graduates of Israeli medical schools in basic and clinical science examinations.

Examinations were used for comparison of Israeli medical school graduates. The two schools with traditional curricula had higher pass rates for first takers of Day 1 (68% and 61%, mean scores 76.6 and 76.4) than the community-based school (44%, mean score 74.5) and the technologically oriented school (40%, mean score 72.5). There were similar pass rates for traditional school first takers of Day 2 (97% and 91%, mean scores 82.4 and 80.4) as for community-based school first takers (94%, mean score 80.1). The traditional schools and the community-based school demonstrated higher pass rates and mean scores for first takers of Day 2 than the technologically oriented school. Analysis of the time lapse between the basic science curriculum and taking the basic science examination reveals no trend in scores or pass rates. While the likelihood of better performance on Day 1 seems enhanced by traditional curricula, there is an equivalent performance on Day 2 by graduates of schools with traditional curricula.

Certification↗
PubMed1994

DNA probes and PCR in diagnosis of mycoplasma infections.

Laboratory diagnosis of mycoplasma infections is hampered by the difficulty or total failure to cultivate the organisms in vitro, and by the frequently weak and poorly specific serological response of the host. DNA probes consisting of cloned ribosomal RNA genes, cDNA to mycoplasmal rRNA, synthetic 16S rRNA oligonucleotide sequences, or cloned mycoplasmal protein genes, have been developed and applied as diagnostic tools in a variety of human and animal mycoplasma infections. These included primary atypical pneumonia caused by Mycoplasma pneumoniae, urogenital infections associated with M. genitalium and Ureaplasma urealyticum, and infections with M. fermentans, M. penetrans or M. pirum--mycoplasmas recently incriminated as cofactors in AIDS. DNA probes were also designed to aid in diagnosis of mycoplasma diseases of farm and laboratory animals, and the hard-to-diagnose mycoplasma infections of cell cultures. Sensitivity of mycoplasma detection by the different probes ranged between 10(3) and 10(6) colony-forming units, a level which may not be sufficiently high for use in a clinical laboratory. The introduction of PCR has pushed aside the previously developed DNA probes, by providing faster and much more sensitive tests. The sensitive level of a PCR test can be as low as a single organism, enabling detection of mycoplasmas in patients treated with antibiotics and in asymptomatic patients. PCR becomes positive prior to serological response and is also effective in immunocompromised hosts. PCR was shown to be most valuable in detection and identification of the non-culturable plant and insect mycoplasma-like organisms (MLOs). Nevertheless, false-negative PCR results are rather common due to inhibitors of the PCR reaction in the clinical specimen, while false-positive results may occur due to contamination of the reagents with target DNA. In conclusion, the PCR procedure is still too complex to be carried out in a routine diagnostic laboratory. PCR prepackaged quality-controlled diagnostic kits are now in the process of rapid development. Once these kits become available, and at a reasonable cost, PCR will certainly take its place as a major diagnostic tool in the routine diagnosis of mycoplasma infections.

Animals↗
PubMed1992

Peculiar properties of mycoplasmas: the smallest self-replicating prokaryotes.

Mycoplasmas are the smallest and simplest prokaryotes capable of self-replication, with information provided by a genome which may be as small as 600 kb, estimated to carry less than 500 genes. Keeping the number of structural elements, metabolic pathways and components of the protein synthesizing machinery to an essential minimum places mycoplasmas closest to the concept of 'minimum cells'. Mycoplasmas are, therefore, most adequate candidates for the complete deciphering of the machinery of a self-replicating organism, and studies towards this goal are already underway. Living as 'minimum cells' was made possible by adopting a parasitic mode of life, securing from the host the many nutrients which cannot be synthesized by the mycoplasmas themselves. When pathogenic, infections by mycoplasmas usually follow a chronic course, with host immune reactions playing an important role in symptom production. Recent studies on the possible association of mycoplasmas with rheumatoid arthritis and AIDS are reviewed.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Nucleotide sequence and codon usage of the elongation factor Tu(EF-Tu) gene from Mycoplasma pneumoniae.

The Mycoplasma pneumoniae tuf gene, encoding the elongation factor protein Tu, was cloned and sequenced. The nucleotide sequence of the mycoplasmal gene showed about 60% homology to the sequences of tuf genes of other prokaryotes, yeast mitochondria and Euglena gracilis chloroplasts, and about 75% similarity was found when comparing the deduced amino acid sequences of the various Tu proteins. The relatively low G + C content (40%) of the M. pneumoniae DNA was reflected in a low G + C content (44.6%) of the tuf gene, and in a preferential use of adenine and uracil at the third position of codons, yet codon usage analysis revealed the presence of almost all of the codons of the genetic code in the mycoplasmal gene. Southern blot hybridization of digested DNAs of 11 Mollicutes species with the entire M. pneumoniae tuf gene and with its 5' part suggested the presence of one copy only of this gene in the representative species of the Mollicutes. In this respect, the Mollicutes resemble Gram-positive bacteria and differ from the Gram-negative bacteria, which carry two copies of the tuf gene.

Amino Acid Sequence↗
PubMed1989

DNA probes for Mycoplasma gallisepticum and Mycoplasma synoviae: application in experimentally infected chickens.

DNA probes specific for Mycoplasma gallisepticum and M. synoviae were selected from genomic libraries prepared in the pUC13 vector. The probes hybridized with the DNA of a wide spectrum of strains within each homologous species, but did not react with the heterologous species or with DNA from any other avian mycoplasma or bacteria tested. Experimental infection and contact exposure of chickens to M. gallisepticum served as models to test the effectiveness of the DNA probe in diagnosis as compared with serological and culture detection methods carried out in parallel. A correlation was generally found between the level of M. gallisepticum in tracheal swabs and the effectiveness of the probe, although a predictably reactive level of mycoplasmas was not always detected. Treatment of clinical specimens with acetylcysteine to disrupt mucus improved the detection rate. Dot-blot hybridization with probe pMG4 enabled positive identification of M. gallisepticum at an early stage of infection, prior to the development of a serological response in the infected chicken. Results are obtainable within 4 days of sampling, much more rapidly than culture, and also in clinical specimens from which mycoplasma isolation is impossible, such as carcasses. The results indicate that the use of DNA probes for the early and rapid detection of M. gallisepticum infection is feasible; a development which can replace laborious culture techniques and less effective serological methods, and thus reduce the time required for diagnosis.

Animals↗
PubMed1989

Genetic and antigenic relatedness between Mycoplasma gallisepticum and Mycoplasma synoviae.

The two avian pathogens Mycoplasma gallisepticum and Mycoplasma synoviae were found, by Southern blot hybridization of their digested DNAs, to share genomic nucleotide sequences additional to those of the highly conserved ribosomal RNA genes. The assumption that some of the shared sequences encode for antigens or epitopes common to both mycoplasmas was supported by Western immunoblot analysis of cell proteins of one mycoplasma with specific antiserum to the other mycoplasma. Interestingly, the band patterns of reactive antigens were different for some of the M. gallisepticum strains, supporting the concept that the species is genotypically variable. The results of the present study may explain the cross-reactivity of the two mycoplasmas noted previously in a variety of routine serological tests.

Animals↗
PubMed1989

Duplication of the tuf gene: a new insight into the phylogeny of eubacteria.

The conservation and duplication of the tuf gene encoding the elongation factor EF-Tu were used to define phylogenetic relationships among eubacteria. When the tufA gene of Escherichia coli was used as a probe in hybridization experiments, duplicate tuf genes were found in gram-negative bacteria from three major phyla: purple bacteria, bacteroides, and cyanobacteria. Only a single copy of tuf was found in gram-positive bacteria, including mycobacteria and mycoplasmas. Gram-positive clostridia were found to carry two copies of tuf.

Bacteroides↗
PubMed1989

Chemiprobe, a nonradioactive system for labeling nucleic acid. Principles and applications.

The Chemiprobe Kit provides a complete system for nonradioactive labeling of DNA probes and their detection in hybridization studies. The system is highly sensitive, permitting the detection of 0.2-0.4 pg DNA which allows detection of a single gene sequence in 0.5-1 microgram of bacterial DNA or in 3-5 micrograms of mammalian DNA. In this paper the authors show that the rRNA genes of M. capricolum can be detected by using only 50 ng/ml of sulfonated probe cloned from another mycoplasma, M. pneumoniae. The Chemiprobe system has been successfully used in the detection of the single copy human gene for glucocerobrosidase from total embryonic DNA by hybridization to a specific sulfonated cDNA. 5 x 10(4) M. pneumoniae cells can be detected either free or mixed with sputum using a standard dot blot technique: mycoplasma cells were lysed by a mucolytic agent, denaturated by NaOH, immobilized on a nylon membrane filter, and then hybridized with pPN4, a plasmid DNA probe specific for M. pneumoniae. The resulting hybrids were then detected by the standard Chemiprobe procedure. A new kit based on the Chemiprobe system has been designed especially for the detection of mycoplasmas in tissue culture. This kit has been tested on 70 random samples collected from tissue culture fluids from 11 different sources. Of these, 42 were found to be contaminated by the Chemiprobe procedure, whereas 41 were found to be contaminated by classical microbiological methods. No false negatives were found.

DNA↗
PubMed1988

Promoters of Mycoplasma capricolum ribosomal RNA operons: identical activities but different regulation in homologous and heterologous cells.

The 5' region of the rRNA operon, rrnA, of M. capricolum was cloned. Sequence analysis revealed two tRNA genes, tRNA(leu) and tRNA(lys), upstream to the promoter of the rRNA operon. The in vivo transcription start sites of the rRNA operon and of the tRNA genes were mapped. The same promoters used by M. capricolum RNA polymerase are also recognized by E. coli RNA polymerase both in vivo and in vitro. We find that high levels of ppGpp in E. coli, resulting from amino acid starvation or from spoT mutation, activate rather than repress the transcription of the mycoplasma rrnA operon.

Base Sequence↗
PubMed1988

Isolation and characterization of stable nuclear matrix preparations and associated DNA from avian erythroblasts.

A novel procedure for isolation of nuclear matrices from chicken erythroblast cells was elaborated. The influence of variations in the isolation procedure on structural integrity and morphology of nuclear matrices as well as on properties of the nuclear matrix-associated DNA fractions was investigated. The incubation of isolated nuclei in the presence of Cu2+ ions provided significant stabilization of the nuclear matrix. Copper treatment of nuclei did not affect the properties of the nuclear skeleton-associated DNA fraction. In both copper-stabilized as well as unstabilized nuclei, nuclear matrix-attached DNA was digested to the same extent with nucleolytic enzymes, and could be totally removed from nuclear matrices by 2 M NaCl-2 M urea treatment. The fine morphology of the nuclear matrix did not change after extraction of nuclear skeleton-associated DNA fragments. In the presence or absence of copper ions, matrix DNA was found to be qualitatively different compared with total DNA, in particular with respect to the representation of specific repetitive sequences of the chicken beta globin gene domain.

Animals↗
PubMed1988

Parameters of Mycoplasma pneumoniae infection in Syrian hamsters.

An animal model for evaluating the potency of Mycoplasma pneumoniae vaccines was developed with hamsters. Factors that influence hamster infection by M. pneumoniae were defined, and parameters for assessment of intensity of pulmonary disease were established. Colonization of hamster lungs was determined by culture, and intensity of lung disease was assessed histopathologically and expressed numerically as a lung pathological score. Intratracheal inoculation of the challenge was superior to the intranasal or aerosol route for inducing a consistent degree of lung disease. A challenge dose of 10(6) CFU inoculated intratracheally produced lung colonization and significant reproducible lung pathological scores in essentially all unvaccinated animals. The peak of infection, as determined by these criteria, was at about 2 weeks after challenge. Animals over 6 weeks of age were preferable for the test, since younger animals exhibited a lower lung pathological score even though they showed the same degree of lung colonization. The hamster assay developed provides a dependable experimental system for testing the protective potency of M. pneumoniae vaccines.

Administration, Inhalation↗
PubMed1988

Hamster challenge potency assay for evaluation of Mycoplasma pneumoniae vaccines.

A hamster immunization challenge assay described in the accompanying paper (M. F. Barile, D. K. F. Chandler, H. Yoshida, M. W. Grabowski, R. Harasawa, and S. Razin, Infect. Immun. 56:2443-2449, 1988) was used to examine protection against Mycoplasma pneumoniae disease by passive immunization and to evaluate the protective potency of a Formalin-inactivated whole-cell and a cell extract M. pneumoniae vaccine. Passive immunization with a globulin fraction of hyperimmune mule antiserum to M. pneumoniae provided hamsters some protection against the challenge. When hamsters were actively immunized, a single dose of Formalin-inactivated vaccine provided only minimal protection, whereas multiple doses of this vaccine, particularly when combined with adjuvant, provided good protection. A single dose of the cell extract vaccine did not protect animals, but two doses caused a marked reduction of disease when a priming dose was given intraperitoneally, followed by a booster dose intratracheally. The correlation between the level of metabolism inhibition antibodies to M. pneumoniae in the sera of vaccinated hamsters and the degree of protection as measured by reduction of lung pathological scores and colonization was poor, indicating that seroconversion rates for metabolism inhibition antibodies are not by themselves adequate to measure the potency of M. pneumoniae vaccines.

Animals↗
PubMed1988

Characteristics of Ureaplasma urealyticum urease.

Sonication of Ureaplasma urealyticum cells grown in a dialysate growth medium effectively separated the cytoplasmic fraction from the membrane fraction, with both fractions relatively free from exogenous contaminating proteins. The urease activity was associated with the cytoplasmic fraction, and the ureaplasmal urease exhibited a specific activity higher than that of crystalline jack bean urease. The enzymatic activity of the ureaplasmal enzyme was optimum at pH 7.5 and was resistant to the chelating agents EDTA and sodium citrate. Sulfhydryl-blocking agents such as HgCl2 and Pb(NO3)2 inhibited the ureaplasmal urease, which was also shown to be particularly sensitive to flurofamide and, to a much lesser extent, to acetohydroxamic acid. Electrophoretic analysis of the proteins of the ureaplasmal cell fractions combined with Western immunoblot with an antiserum to the ureaplasmal urease indicated that the urease constitutes a major component of the cytoplasm and is composed of several 70-kilodalton polypeptides.

Citrates↗