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  • 1
    ISSN: 1573-5036
    Keywords: Alyssum ; cobalt uptake ; germination tests ; hyperaccumulators ; copper uptake ; nickel uptake ; plants ; toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The uptake of Ni, Co, and Cu by the nickel hyperaccumulator Alyssum troodii Boiss and the non-accumulator Aurinia saxatilis (L.) Desv. were studied in pot trials using artificial rooting media with varying concentrations of the metals added as soluble salts, singly and in combination. The ability of five other Ni hyperaccumulating species of Alyssum to hyperaccumulate Co was also investigated. Leaves and stems of A. troodii accumulated Ni to almost the same extent (8000–10 000 μg g-1). In roots, the highest Ni concentration was 2000 μg g-1. In leaves of Au. saxatilis, the maximum Ni concentration was only 380 μg g-1 and the level in roots was even lower. In media containing Co, the maximum concentration of this element in A. troodii (2325 μg g-1) was ten times higher than in the non-accumulator species. Slightly less Co was found in stems and roots of both species. Among the other Ni hyperaccumulators, the maximum concentration of Co in leaves ranged from about 1000–8000 μg g-1. Copper concentrations were the same in all organs of both species when they were grown in copper-rich media and were in the range 40–80 μg g-1, showing that neither plant was capable of taking up Cu at levels comparable to those of Ni and Co. When both plants were grown in media containing equal amounts of both Co and Ni, the Co concentrations in plant organs were the same as for specimens grown in media containing Co only. However, the Ni levels were lower in both species. Uptake of Co therefore appeared to suppress Ni uptake. Pot trials showed that the order of tolerance was Ni〉Cu〉Co for A. troodii and Ni〉Co≈Cu for Au. saxatilis, whereas the seedling tests showed the order to be Co〉Ni〉Cu. At metal concentrations ≥10 000 μg g-1, the overall tolerance of A. troodii was greater than that of Au. saxatilis which exhibited equally low tolerance to Ni and Cu. We conclude that in A. troodii, A. corsicum Duby, A. heldreichii Hausskn., A. murale Waldstein & Kitaibel, A. pintodasilvae T.R. Dudley, and A. tenium Hálácsy, Ni tolerance and hyperaccumulation conveys the same character towards Co. This behaviour should be investigated in other hyperaccumulators of Ni and/or Co.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 86 (1975), S. 369-377 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: After the re-addition of serum in the presence of adenosine (25 m̈M), the entry of quiescent, serum starved BHK 21 cells into DNA synthesis follows first order kinetics after a well defined lag period of eight hours, and with a rate constant dependent on serum concentration. Initiation of DNA synthesis under these conditions can therefore be considered to be a random event occurring with a “Transition Probability” determined by the serum concentration. In the presence of adenosine, the change of Transition Probability following the addition of serum occurs abruptly. In the absence of exogenous adenosine, however, the change of Transition Probability after serum addition appears to be both gradual and bi-phasic. The initial changes in the absence of adenosine, though smaller in magnitude, display a similar dependence on serum concentration to the changes occurring in the presence of the nucleoside. In contrast, the secondary gradual increase of Transition Probability in the absence of added purines exhibits a higher serum requirement. It is suggested that the regulation of Transition Probability by serum involves some purine-dependent process, and that in the absence of an exogenous supply this becomes limited by endogenous synthesis which in turn may be dependent on serum concentration.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 121 (1984), S. 547-557 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The growth factors FGF and vasopressin were found to have only a transient effect on confluent quiescent monolayers of Swiss 3T3 cells. Whether measured as cumulative entry into S-phase by autoradiography, or as cell division by time-lapse filming, the elevated rate of cell proliferation was maintained only over 10-15 hr. Several trivial or artifactual explanations for this transience were ruled out, including toxicity of 3H-thymidine; exhaustion or degradation of medium components, nutrients or growth factors (although some medium depletion was observed); and the generation during quiescence of cells incapable of division. We have also eliminated heritable variation in the capacity to respond to individual growth factors. However, unstable phenotypic heterogeneity in growth factor requirements between cells may play some part, as found elsewhere for the response to low concentrations of serum (Brooks et al, 1984). Cell populations that had ceased to respond to vasopressin recovered their sensitivity after 2-3 days' incubation in conditioned medium lacking vasopressin. The phenomenon thus resembles the mitogen-induced desensitization described by Collins and Rosengurt (1982, 1983). However, in our case, the loss of sensitivity was not selective for vasopressin but applied also to epidermal growth factor (EGF) and to prostaglandin F2α. Furthermore, changes in responsiveness to vasopressin with time were associated with changes in cell density. Although some element of selective desensitization has not been ruled out, the transient response in our experiments can be accounted for in terms of unstable heterogeneity in growth factor requirements and/or in terms of density-dependent regulation of growth.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    BioEssays 11 (1989), S. 35-38 
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The following is a report of a meeting of the British Society for Cell Biology on ‘The Cell Cycle’, at St Andrews University, 4-6 April, 1989.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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