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  • 1
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    German Medical Science GMS Publishing House; Düsseldorf
    In:  88. Jahresversammlung der Deutschen Gesellschaft für Hals-Nasen-Ohren-Heilkunde, Kopf- und Hals-Chirurgie; 20170524-20170527; Erfurt; DOC17hno163 /20170413/
    Publication Date: 2017-04-13
    Keywords: ddc: 610
    Language: German
    Type: conferenceObject
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  • 2
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In most patients with chronic hepatitis B positive for antibodies (anti-HBe) to HBe antigen (HBeAg), a pre-core mutant hepatitis B virus (HBV) with a point-mutation at nt. 1896 can be isolated. Clinical significance of the mutant virus in chronic hepatitis B is not proven yet, and screening of large numbers of sera during different clinical courses of numerous patients is necessary. We therefore aimed to develop a fast and reliable assay, that allows to discriminate wildtype from nt. 1896 G → A mutant HBV and to determine the ratio of mutant and wildtype HBV in patients' sera. A mutation specific polymerase chain reaction (ms PCR) with new primers served to distinguish nt. 1896 G → A mutant from wildtype HBV. This msPCR proved to be more sensitive and specific than similar assays described previously. When compared to a dilution series of a cloned HBV-DNA standard, the amount of wildtype and nt. 1896 G → A mutant HBV could be determined semiquantitatively. 102 to 107 copies of each HBV-DNA (equivalent to 105 to 1010 copies of HBV-DNA/ml patients' serum) could be amplified with steadily increasing signals. MsPCR proved to be specific as 107 copies did not give an amplification signal if they did not match the respective primer pair used. In a mixed population of mutant and wildtype virus, msPCR allows to detect even a low amount of the minor HBV strain (0.1–0.01%, of the viral population) and to determine the ratio of wildtype and mutant HBV. MsPCR is as fast and convenient to perform as an unmodified PCR. It requires careful performance to avoid contamination but no specific equipment. Clinical usefulness of msPCR was demonstrated when the ratio of wildtype to mutant HBV was determined in 86 sera collected during 3 to 7.5 years follow up of 9 patients suffering from anti-HBe positive chronic hepatitis B. We conclude that this assay conveniently allows to study patients with chronic hepatitis B in order to detect and follow-up the emergence of pre-core stop-codon mutant HBV in correlation to the clinical course.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary.  Quantification of serum HCV-RNA and HCV genotyping was studied in 27 patients with chronic hepatitis C undergoing interferon treatment. Pretreatment serum HCV-RNA levels were quantified using competitive RT-PCR and compared to a quantitative RT-PCR assay based on co-amplification of HCV-RNA with a synthetic RNA standard. HCV genotyping was performed using a line probe reversed hybridisation assay or direct solid-phase sequencing. This study shows the feasibility of performing HCV-RNA quantification. RT-PCR based on co-amplification HCV-RNA titer less than 6× 104 genome equivalents/ml serum did correlate with a complete sustained response to α interferon in chronic hepatitis C. HCV genotype 1b was α predominantly associated with a high non-responder rate. Future prospective trials will be required to evaluate quantitative HCV-RNA levels and HCV genotyping as response predicting parameters for interferon-treatment.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 98 (1966), S. 278-286 
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Pre-infection of cells (grown in nutrient broth) with the fr mutant A105 resulted in partial exclusion of superinfecting fr, as determined with single burst experiments. The extent of exclusion increased with the time interval between A105- and fr-input. Pre-infection of cells (grown in yeast tryptone broth) with fr suppressed the formation of superinfecting A105, pre-infection with A105 however did not suppress the formation of superinfecting fr (determined as serum-resistant PFU). Simultaneous infection of cells, grown in yeast tryptone broth, with fr and A105 showed in single-burst experiments double infection to occur: 50% of the single bursts contained both plaque types. Rescue of the host-dependent f2 mutants su-1 and su-3 could be demonstrated with the fr mutant A105. With su-1, rescue could only be demonstrated if cells were simultaneously infected or if A105 preceeded su-1. Pre-infection with su-1 resulted in exclusion of A105. With su-3 the reverse was found: pre-infection with A105 resulted in exclusion of the f2 mutant, pre-infection with su-3 permitted rescue with A105. Removal of unadsorbed phages between inputs did not influence the yield of rescued phage.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A variety of conditions caused both, the f+ antigen and fr-receptor sites of E. coli strains to appear or disappear simultaneously: Both characters were lost after temperature-downshift, they were recovered after temperature-upshift; fr-refractory mutants failed to absorb f+ antibodies. Strains, genetically labelled with an Flac+ episome permitted the differentiation of an episomal and a chromosomal lesion, both of which affected the receptor site for fr, and at least one of which (episomal lesion) affected the formation of the f+ antigen as well. (In addition, strains lacking fr receptors had exhibited a significant reduction of their capacity to form recombinants.) The results provide strong correlative evidence for the identity of the f+ antigen and the cellular receptor for fr. The results provide additional evidence for the identity of the phage- and the mating-specific sites on E. coli.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 98 (1966), S. 270-277 
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Interference could be demonstrated to occur between fr- and f2-mutants, indicating that the observed effect of mutual exclusion between fr+ and fr-A 105 is of general nature. Phage lysates, inactivated during storage at 4o, showed strong interference with homologous phages. This phenomenon may serve as an explanation for the “temporary immunity” of fr-sensitive cells. UV-inactivated phages interfered with superinfecting viable phages if present at low input multiplicity. This interference showed a maximum of expression immediately upon mixing cells with inactivated phages. During the subsequent 15 min the amount of interference decreased and stayed constant from then on. Cells, pre-treated with UV-inactivated phages permitted the adsorption of challenge virus, not however its invasion.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 98 (1966), S. 180-186 
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Phage fr is able to multiply adsorb to host cells (E. coli K 12, strain 3300). Single burst analysis of cells infected with a mixture of fr+ and its plaque mutant fr-A105 revealed that tubes containing both plaque types were found in such proportion as would be expected under the assumption of mutual exclusion. If one of the phages was permitted to preadsorb for 5 min with an input multiplicity of〉10, followed by a second phage type, for another 5 min adsorption period, exclusion of the second phage was found.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 198 (1963), S. 97-97 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Table 1. COMPARISON OF THE INACTIVATION-RATE BY NITROUS ACID OF PHAGE fr AND OTHER VIRUSES Virus Temperature NaN02 Reference material ( C) pTL (molarity) t TMV 22 4-2 1-0 23 9 TMV-BNS 22 4-5 1-0 8-5 9 Using the pre-adsorption technique platings of phage fr always showed a few smaller plaques ...
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0005-2787
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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