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  • 1
    Electronic Resource
    Electronic Resource
    Disktron accelerator (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 2466-2474 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new type of low-energy ion accelerator has been developed. It includes an eight-storied Disktron generator, newly developed accelerating tubes which hold up to 4 MV/m, both single and tandem acceleration capability, and a compound negative ion source. The Disktron generates 3.2 MV with a dummy load and 2.2 MV with ion beams, and has a voltage stability better than 10−3 at around 1 MV with a corona feedback stabilizer or a generating voltmeter feedback stabilizer only. The highly stabilized voltage of the Disktron has particularly been allowed to form an ion microbeam of about 1-μm diameter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143905
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  • 2
    Electronic Resource
    Electronic Resource
    Identification and characterization of virK, a virulence-associated large plasmid gene essential for intercellular spreading of Shigella flexneri (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 6 (1992), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Seven virulence loci have been identified by Tn5 insertion mutagenesis on the large 230 kb plasmid (pMYSH6000) of Shigella flexneri 2a. In this study, we used Tn10 insertion mutagenesis and identified a novel virulence locus on pMYSH6000 responsible for bacterial spread. Characterization of the invading bacteria of the Tn10 insertion mutants in the epithelial cells revealed that the bacteria were capable of at least some intracellular spreading but not intercellular spreading. Immunoblot analysis of lysates of the Tn10 insertion mutants with a VirG-specific antipeptide antibody revealed diminished levels of the 116 kDa VirG protein. The virG mRNA in the mutants, however, was expressed at the same level as that in the wild type. The DNA region required for the virulence phenotype was localized to a 1.6 kb DNA sequence in the Sal I-K fragment on the plasmid, and thus the locus was designated virK. Expression of virK in Escherichia coli using a T7 RNA polymerase-dependent promoter system yielded a 36 kDa protein. The nucleotide sequence of 1642 bp encoding VirK function was determined, and an open reading frame encoding 316 amino acid residues was shown to encode the VirK protein. The virK region was highly conserved among the large virulence plasmids of shigellae and enteroinvasive Escherichia coli. These results suggest that VirK function is an essential virulence determinant for shigellae Involved in the expression of virG gene product at post-transcriptional level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1992.tb01413.x
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  • 3
    Electronic Resource
    Electronic Resource
    Construction of a physical map of the chromosome of Shigella flexneri 2a and the direct assignment of nine virulence-associated loci identified by Tn5 insertions (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 5 (1991), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: To establish the molecular basis of the chromosomal virulence genes of Shigella flexneri 2a (YSH6000), a Notl restriction map of the chromosome was constructed by exploiting Notl-linking clones, partial Notl digestion and DNA probes from various genes of Escherichia coli K-12. The map revealed at least three local differences in the placements of genes between YSH6000 and E. coli K-12. Using the additional Notl sites introduced by Tn5 insertion, nine virulence loci Identified previously by random Tn5 insertions were physically mapped on the chromosome. To demonstrate the versatility of the Notl map in direct assignment of the virulence loci tagged by Tn5 to a known genetic region in E. coli K-12, the major class of avirulent mutants defective in the core structure of lipopolysaccharide (LPS) was examined for the sites of Tn5 insertions. The two Notl segments created by the Tn5 insertion in the Notl fragment were analysed by Southern blotting with two DNA probes for the 5′ and 3’flanking regions of the rfa region, and shown to hybridize separately with each of them, confirming the sites of Tn5 in the rfa locus. This approach will facilitate direct comparison of genetically mapped Tn5 insertion mutations of S. flexneri with genes physically determined in E. coli K-12.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1991.tb02147.x
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  • 4
    Electronic Resource
    Electronic Resource
    Functional organization and nucleotide sequence of virulence Region-2 on the large virulence plasmid in Shigella flexneri 2a (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 3 (1989), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The 7kb virulence Region-2 of the large (virulence) plasmid in Shigella flexneri 2a encodes several proteins required for invasion of intestinal epithelial cells. Insertion and deletion mutagenesis, DNA subcloning and SDS-polyacrylamide gel electro-phoresis of proteins synthesized in minicells demonstrated five genes in this region. They encode 24, 18, 62 (lpaB), 41 (lpaC) and 37 (lpaD)-kiloDalton (kD) proteins. Complementation of Tn5-induced mutations in Region-2 with the above plasmid constructs indicated that Region-2 consists of two operons and that the three lpa proteins are essential for the virulence phenotype. The transcriptional organization determined by Northern blotting, S1 nuclease protection and the effect of Tn5 insertions on expression of the lpa proteins revealed that Region-2 has three promoters that transcribe RNAs of 4.0, 4.5 and 7.5kb. The 4.0 kb RNA was the transcript for the operon encoding the 24, 18 kD, lpaB and C proteins and the 4.5 kb RNA for the ipsD gene. In addition, the full-length RNA of 7.5 kb which covers Region-2 supplemented full expression of the lpa proteins. The 7663 nucleotides of Region-2 were determined to confirm the five open reading frames encoding 23655, 17755, 62168, 41077 and 36660 Dalton proteins, respectively, and their regulatory sequences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1989.tb00269.x
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  • 5
    Electronic Resource
    Electronic Resource
    Virulence-associated chromosomal loci of Shigella flexneri identified by random Tn5 insertion mutagenesis (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 5 (1991), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Shigellae are the causative agents of bacillary dysentery and are capable of invading epithelial cells, multiplying therein and spreading into adjacent cells. To identify genes on the chromosome associated with the virulence phenotype, 9114 independent Tn5 insertion mutants were isolated in a virulent strain of Shigella flexneri. By using an in vitro assay for intercellular spread or an animal infection model, the Serény test, 50 chromosomal Tn5 mutants with reduced virulence were identified. The 50 mutants were characterized with respect to their virulence phenotypes, including three different mutations that affect invasion of epithelial cells, bacterial metabolism and structure of lipopolysaccharide. Mutants with reduced invasive ability were further characterized and it was found that two of them had decreased levels of IpaB, C and D antigens as well as the mRNA for the ipaBCD operon encoded by the large virulence plasmid, suggesting that positive regulatory elements for the IpaBCD operon are encoded by the chromosome. Assignment of the 50 Tn5 insertions of the mutants to the 19 Notl restriction fragments of the chromosomal DNA has permitted the identification of at least nine virulence-associated chromosomal loci.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1991.tb01839.x
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  • 6
    Electronic Resource
    Electronic Resource
    Temperature-regulated expression of invasion genes in Shigella flexneri is controlled through the transcriptional activation of the virB gene on the large plasmid (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 5 (1991), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The invasion phenotype of shigellae is subject to thermoregulation that is known to be expressed through activation of some invasion (inv) genes such as ipaB, ipaC, and ipaD encoded by the large virulence plasmid of Shigeila flexneri. The expression of ipa genes is regulated positively by virF through the activation of virB on the plasmid. To identify the mediator for the thermoregulation of the large plasmid, we have studied the effect of temperature on the transcription of virF and virB genes and ipa and the other two inv operons. The results showed that transcription of VirB was affected by temperature more strictly than that of virF. Analysis of the mRNA level of virB at different levels of virF transcription indicated that virB transcription depended upon both temperature and virF. On the other hand, transcriptions of ipa and the other two inv operons depended on the activation of virB transcription but not on temperature. By inducing wr8 transcription from a tac promoter fused with the virB region, invasion ability was restored to a WrF-deletion mutant at 30°C as well as at 37°C. By using conditions in which the temperature-dependent expression of the invasion phenotype was circumvented by the induction of virB transcription, intercellular spreading ability in a virF+, virB::Tn5 strain was shown to be expressed even at 30°C. These results suggest that the virB transcription stage is the main target for the thermoregulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1991.tb00762.x
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular cloning and characterization of chromosomal virulence region kcpA of Shigella flexneri (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 3 (1989), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In Shigella flexneri, in addition to several well-recognized plasmid-borne virulence loci, at least three genetic loci implicated in pathogenesis have been recognized on the chromosome. To understand more about the pathogenesis of bacillary dysentery at a molecular level, the genetically recognized but previously unidentified KcpA region (one of the chromosomal regions near purE) was cloned and sequenced. A single translatable open reading frame encoding a 12310 Dalton protein corresponding to the minicell product was found. Immunofluorescence microscopy, as well as optical and electron microscopic comparison of tissue-cultured cells and guinea-pigs’eyes infected with wild-type or kcpA mutant bacteria, revealed that the kcpA product is required by invading bacteria for spread into adjacent cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1989.tb01809.x
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  • 8
    Electronic Resource
    Electronic Resource
    Corticosteroid treatment of diffuse mesangial proliferative IgA nephropathy (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Nephrology 4 (1998), S. 0 
    Details
    ISSN: 1440-1797
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1797.1998.tb00448.x
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  • 9
    Electronic Resource
    Electronic Resource
    Eicosapentaenoic acid-induced changes in membrane fluidity and cell adhesion molecules in cultured human keratinocytes (1995)
    Oxford, UK : Blackwell Publishing Ltd
    British journal of dermatology 133 (1995), S. 0 
    Details
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The effects of eicosapentaenoic acid (EPA, 20:5n-3) on the lipid dynamics of cultured epidermal keratinocytes and their expression of cell adhesion molecules were investigated, and were compared with those of arachidonic acid (AA, 20:4n-6). When keratinocytes were treated with 3 μg/ml of EPA or AA for 72 h, these compounds were found to be incorporated into the cells. EPA-induced lipid changes were distinguished by a significant increase in the cellular content of n-3 polyunsaturated fatty acids, whereas AA treatment resulted in an increase in the cellular content of n-6 arachidonic acid. These changes in fatty acid composition were accompanied by an increase in cellular membrane fluidity, which was evaluated by the diffusion coefficient, using the method of fluorescence recovery after photobleaching (FRAP) [from 1–77±0–34 × 10−8cm2/s untreated to 2–23±0–35 × l0−8cm2/s EPA-treated (P 〈 0.001), and 2–16±0–35 × 10−8cm2/s AA-treated (P 〈 0·001)]. Intercellular adhesion molecule-1 (ICAM-1) was induced on the keratinocyte membrane in the presence of tumour necrosis factor-a and interferon-γ, and pretreatment with EPA or AA further enhanced the expression, almost to an equal degree, as estimated by flow cytometry (P 〈 0.05). These results indicate that the modulation of ICAM-1 expression does not seem to be EPA-specific, but is presumably a consequence of increased membrane fluidity due to the increased levels of unsaturated fatty acids of both the n-3 and n-6 series in the membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2133.1995.tb02618.x
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  • 10
    Electronic Resource
    Electronic Resource
    Characterization of pigmented granules in minocycline-induced cutaneous pigmentation: observations using fluorescence microscopy and high-performance liquid chromatography (1993)
    Oxford, UK : Blackwell Publishing Ltd
    British journal of dermatology 129 (1993), S. 0 
    Details
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We describe a technique to facilitate histopathological detection and quantitative measurement of trace amounts of tissue minocycline.In a patient with minocycline-induced hyperpigmentation, a series of biopsies were taken from the affected skin over a period of 54 months, and examined for tissue minocyclinc deposition. Frozen sections treated with 1 m MgCl2-ethanol yielded minocycline-specific yellowish fluorescence, the location of which corresponded to clumps of granular deposits in the dermis. A decrease in the number of fluorescent granules correlated with the clinical resolution of hyperpigmentation and a significant decrease in the tissue minocycline level. Our data also provide further support for the concept that the pigment granules contain insoluble complexes of minocycline chelated with iron. The fluorescence technique is simple, sensitive, and reproducible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2133.1993.tb03166.x
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