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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Inorganic chemistry 32 (1993), S. 3099-3103 
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Pedospheric nitrate uptake is a strongly regulated process adapted to the N demand of the whole plant. Pre-requisites for an integrating regulatory system are signal substances communicating the N demand of the shoot to the roots. In the current study it was shown that an additional atmospheric N source results in activation of cytokinins in the shoot as indicated by an increase in the trans-hydroxylation ratio, and in increased shoot-to-root transport of cytokinins in the phloem. Phloem mobility and basipetal transport of cytokinins were also demonstrated by feeding zeatin riboside into the phloem. The resulting enrichment of cytokinins in the roots caused an increased expression of a high-affinity nitrate transporter, the enrichment of amino compounds (Glu, Val, Phe, Lys) in the fine roots and a significant decrease in nitrate net uptake. Significant enrichment in amino acids – accompanied by decreased nitrate net uptake but not by increased expression of the high-affinity nitrate transporter – was also observed when Gln the major long-distance transport form of nitrogen in beech was fed into the phloem. These results provide experimental evidence that, in addition to amino compounds, cytokinins that are known to cycle within the plant are also communicating changes in N metabolism from the shoot to the roots. Apparently increased cytokinin contents in the root can transiently increase nitrate uptake, but this up-regulation may be overridden by transcriptional and post-transcriptional down-regulation mediated by amino compounds.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 26 (2003), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Previous work has shown that conifers growing on sites exposed to aerial pollution exhibit a different pattern of vegetative development in comparison with those on unpolluted sites, and have higher needle cytokinin contents (von Schwartzenberg & Hahn, Journal of Plant Physiology 139, 218–223, 1991). Physiologically mature Sitka spruce (Picea sitchensis[Bong.] Carr) trees growing in a commercial plantation were sprayed with combinations of S, N and acidity from bud burst until December, for a 3 year period, in order to factor out the effects of individual pollutants and identify the specific component responsible for the high cytokinin content. Cytokinins were monitored using high-performance liquid chromatography/enzyme-linked immunosorbent assay techniques. After 3 years of treatment only needles of neutral N-treated trees contained significantly higher levels of cytokinin than those of trees receiving no spray. The addition of acid S could suppress the effects of added N. Needles from neutral N treatments also contained significantly higher levels of biologically active cytokinins and forms that can be transported in the xylem/phloem. Significantly lower levels of active cytokinins were present in needles sprayed with N in combination with acid sulphate. The results demonstrate that the needle cytokinin content may be used as a sensitive and selective bioindicator of the early stages in N perturbation in coniferous trees.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0968-0004
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Polyhedron 12 (1993), S. 1-5 
    ISSN: 0277-5387
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 313 (1985), S. 64-67 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A proportion of the Con A monomer extracted from mature seeds is cleaved after Asn 118 (ref. 4), yielding three bands on SDS-polyacrylamide gel electrophoresis (PAGE) (Fig. 1B). An initial observation that some of the monomer extracted from immature seeds had a slightly higher relative molecular ...
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  • 7
    ISSN: 1432-1173
    Keywords: Schlüsselwörter UV-Schutzfaktor ; Kleidung ; Sonnenschutz ; Prävention ; Key words Fabrics ; Clothes ; Sun protection ; Prevention ; Skin cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary A rising incidence worldwide of skin cancer has been observed for years. A high cumulative exposure to UV radiation is a major factor in the development of such neoplasms. Suitable protective measures are therefore becoming increasingly important. Textiles provide simple, effective and medically safe protection against UV radiation. At present, however, in Europe – in contrat to Australia – the UV protection factor (UPF) for summer textiles is not stated. It is a largely unknown fact that by far not all textiles offer sufficient protection. Our goal was to study the factors which determine the UV transmission of fabrics and, based on these findings, to design materials which provide enhanced protection. A spectrophotometric method was used to determine the UV transmission by fabrics made of cotton, silk, polyester and viscose. The UV protection factors of the fabrics were computed on the basis of the transmission data. The UV protection factor is dependent on the type of fibre, yarn and surface design, weight per square metre, moisture content, colour, finishing method and degree of wear. To optimize the UV protection via textiles, a viscose yarn with a low UV transmission was used. This yarn makes it possible to design light-weight summer fabrics with optimized UV protection. This development will make it possible to offer clothing with high UV protection on the European marked. This clothing will not be more expensive than normal products, so that effective prevention should be more available.
    Notes: Zusammenfassung Seit Jahren wird ein weltweiter Anstieg der Hautkrebsinzidenz beobachtet. Eine hohe kumulative UV-Strahlenexposition gilt als ein Hauptfaktor für die Entstehung von Neoplasien der Haut. Geeignete Schutzmaßnahmen gewinnen daher zunehmend an Bedeutung. Textilien bieten eine einfachen und effektiven, medizinisch unbedenklichen Schutz vor der UV-Strahlung, doch wird der UV-Schutzfaktor (USF) von Sommertextilien, z.Z. in Europa – im Gegensatz zu Australien – nicht angegeben.Weitgehend unbekannt ist in diesem Zusammenhang, daß bei weitem nicht alle Textilien einen ausreichenden Schutz bieten. Ziel ist, die Faktoren, welche die UV-Durchlässigkeit von Stoffen bestimmen, zu untersuchen und ausgehend von diesen Ergebnissen Materialien mit verbessertem Schutz zu konstruieren. Die UV-Durchlässigkeit wurde an Geweben aus Baumwolle, Seide, Polyester und Viskose mit einer spektralphotometrischen Methode bestimmt. Die UV-Schutzfaktoren der Stoffe wurden aus den Transmissionsdaten berechnet. Anhand der Ergebnisse konnte gezeigt werden, daß UV-Schutzfaktor von der Faserart, der Garn- und Flächenkonstruktion, dem Quadratmetergewicht, dem Feuchtegehalt, der Färbung, der Ausrüstung und der Abnutzung durch den Gebrauch der Stoffe abhängt. Zur Optimierung des UV-Schutzes durch Stoffe wurde erstmals ein Viskosegarn mit einer extrem geringen UV-Durchlässigkeit eingesetzt. Dieses Garn ermöglicht es, leichte Sommerstoffe mit optimiertem UV-Schutz zu konstruieren. Zukünftig wird es damit möglich sein, Kleidung mit einem hohen UV-Schutzfaktor anzubieten. Diese Kleidung wird nicht teurer sein als normale Produkte, so daß eine hohe Effektivität für unsere Präventionsbemühungen erwartet werden kann.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Planta 165 (1985), S. 359-365 
    ISSN: 1432-2048
    Keywords: Bud dormancy ; Chilling ; Cytokinin and dormancy ; Solanum (bud dormancy) ; Tuber storage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Potato (Solanum tuberosum L.) tuber buds normally remain dormant through the growing season until several weeks after harvest. In the cultivar Majestic, this innate dormancy persisted for 9 to 12 weeks in storage at 10° C, but only 3 to 4 weeks when the tubers were stored at 2° C. At certain stages, supplying cytokinins to tubers with innately dormant buds induced sprout growth within 2 d. The growth rate was comparable to that of buds whose innate dormancy had been lost naturally. Cytokinin-treatment did not accelerate the rates of cell division and cell expansion in buds whose innate dormancy had already broken naturally. Gibberellic acid did not induce sprout growth in buds with innate dormancy. We conclude that cytokinins may well be the primary factor in the switch from innate dormancy to the non-dormant state in potato tuber buds, but probably do not control the subsequent sprout growth.
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  • 9
    ISSN: 1432-2048
    Keywords: Bud dormancy (innate) ; Cytokinin metabolism ; Solanum (bud dormancy)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A radioimmunoassay, combined with high-performance liquid chromatography, has been used to analyse the zeatin-type cytokinins of potato (Solanum tuberosum L. cv. Majestic) tubers and tuber buds throughout growth and storage. During tuber growth, zeatin riboside was the predominant cytokinin detected in all tissues. Immediately after harvest, the total cytokinin concentration fell dramatically in the storage tissue, largely as a consequence of the disappearance of zeatin riboside. During storage, levels of cytokinins in the storage tissue remained relatively constant, but increased in the tuber buds. In the buds of tubers stored at 2°C there was a 20-to 50-fold increase in total cytokinin over six weeks, coinciding with the natural break of innate dormancy. At 10°C the rise in the level of bud cytokinins was slower, correlating with the longer duration of innate dormancy. Injecting unlabelled cytokinins into tubers in amounts known to induce sprouting gave rise to increases in cytokinin concentrations in the buds of the same order as the increase associated with the natural break of dormancy. Metabolism of injected cytokinins was greater in non-dormant than in dormant tubers. The roles of cytokinin concentration and the sensitivity of the buds to cytokinin in the control of dormancy are discussed.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Planta 169 (1986), S. 216-221 
    ISSN: 1432-2048
    Keywords: Callus ; 1,2-Diacylglycerol ; Glycine (phosphatidylinositol) ; Inositol phosphates ; Phosphatidylinositol ; Phospholipase C
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have investigated the breakdown of membrane-bound phosphatidylinositol (PI) in homogenates of soybean (Glycine max) callus. The breakdown of PI was stimulated by the detergent deoxycholate. At pH 7.0 and 1·gl-1 of deoxycholate the loss of PI was rapid and extensive: more than 80% was broken down within 10 min. The breakdown of PI was also stimulated by millimolar concentrations of Ca2+. The products of breakdown of added PI (purified from soybean callus) in this system were identified from their chromatographic mobilities as 1,2-diacylglycerol, myo-inositol 1-phosphate and myo-inositol 1:2-cyclic monophosphate.
    Type of Medium: Electronic Resource
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