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  • 1
    ISSN: 1617-4623
    Keywords: Key wordsAgrobacterium tumefaciens ; Chitinase ; Gene silencing ; Nicotiana sylvestris ; Ti plasmid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Agroinfiltration – the infiltration of Agrobacterium tumefaciens into intact plant leaves – provides a rapid and simple way of screening large numbers of transgene constructs for silencing in response to a resident transgene. Transgenic Nicotiana sylvestris plants homozygous for the tobacco class I chitinase A gene CHN48 under the control of the cauliflower mosaic virus 35S RNA promoter (P35S) show a high incidence of postranscriptional gene silencing. We forced suspensions of A. tumefaciens, carrying P35S-CHN48 in a binary Ti-plasmid vector, into wild-type and transgenic N. sylvestris leaves with a blunt-tipped plastic syringe. The infiltrated CHN48 transgene was expressed in leaves transformed with the vector alone, but not in CHN48-transformed leaves showing the silent phenotype. In contrast, expression of a chimeric P35S-E. coliβ-glucuronidase gene (uidA) infiltrated into leaves was not affected by the presence of the CHN48 transgene stably integrated in the host genome. These results show that extra copies of CHN48 are silenced by resident, silent copies of the same gene and confirm that CHN48 silencing is not the result of promoter interactions. The results also suggest that silencing of the additional CHN48 copies does not require their integration into chromosomes.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Monatsschrift Kinderheilkunde 146 (1998), S. S49 
    ISSN: 1433-0474
    Keywords: Schlüsselwörter Oligosaccharide ; Frauenmilch ; Kuhmilch ; Säuglingsnahrungen ; Infektabwehr ; Zelladhäsionsmoleküle ; Key words Oligosaccharides ; Human milk ; Bovine milk ; Infant formula ; Defense system ; Cell adhesion molecules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary About a century ago paediatricians observed that in the faeces of breast-fed infants, Bifidobacterium bifidum was the predominant microorganism compared to those of bottle-fed infants. It was shown thereafter that aminosugar containing oligosaccharides it contains are growth factors for a specific strain of Bifidobacterium. Meanwhile, more than 130 lactose-derived oligosaccharides have been identified in human milk. Some of these components, such as lacto-N-tetraose and lacto-N-fucopentaose I and II, do not occur in minute amounts but in concentrations up to 1–2 g/l. As the total amount of complex oligosaccharides is between 5 and 8 g/l these components must be considered major human-milk constituents. There is striking evidence that human-milk oligosaccharides are potent inhibitors of bacterial adhesion to epithelial surfaces, an initial stage of infective processes. Therefore, these oligosaccharides are considered to be soluble receptor analogues of epithelial cell surfaces participating in the non-immunological defense system of infants fed with human milk. In addition, they may also influence inflammatory processes by acting as ligands for certain cell-adhesion molecules.
    Notes: Zusammenfassung Um die Jahrhundertwende beobachtete man, daß die Darmflora bei gestillten Kindern im Gegensatz zu der bei sog. Flaschenkindern vorwiegend aus Bifidusbakterien besteht. Mitte der 50er Jahre wurde nachgewiesen, daß Oligosaccharide, die Aminozucker enthalten, das Wachstum eines bestimmten Bifidobakterienstamms fördern. Mittlerweile sind mehr als 130 auf Laktose basierende Oligosaccharide in Frauenmilch charakterisiert worden. Einige dieser Oligosaccharide wie die Lakto-N-Tetraose und die Lakto-N-Fucopentaose I und II kommen nicht nur in Spuren, sondern in Konzentrationen bis 1–2 g/l vor. Die Gesamtkonzentration liegt bei 5–8 g/l, so daß man diese Komponenten zu den Hauptmilchinhaltsstoffen zählen muß. Diskussion: Es gibt immer mehr Hinweise darauf, daß diese Komponenten potentielle Inhibitoren der Anhaftung von pathogenen Bakterien und von Viren an Epithelzellen sind, wodurch der erste Schritt eines Infektionsvorgangs verhindert werden könnte. Daher werden solche Oligosaccharide als lösliche Rezeptoranaloga zu Kohlenhydratstrukturen auf Epithelzellen betrachtet, die möglicherweise zu einer besseren Infektabwehr von frauenmilchernährten Neugeborenen beitragen. Außerdem beeinflussen Oligosaccharide in Frauenmilch möglicherweise entzündliche Reaktionen z.B. im Gastrointestinaltrakt, da sie als lösliche Liganden von Zelladhäsionsmolekülen wirken könnten.
    Type of Medium: Electronic Resource
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