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  • 1
    Electronic Resource
    Electronic Resource
    Glutamine-synthetase isoforms appearing in sunflower cotyledons during germination (1992)
    Springer
    Planta 186 (1992), S. 577-581 
    Details
    ISSN: 1432-2048
    Keywords: Ammonia/ammonium assimilation ; Enzyme regulation ; Glutamine synthetase ; Helianthus (glutamine synthetase) ; Seed germination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ion-exchange chromatography has been used to separate the isoforms of glutamine synthetase (GS; EC 6.3.1.2) appearing in sunflower (Helianthus annuus L. cv. Peredovic) cotyledons during seedling growth under different light and nitrogen conditions. Both in dry and imbibed seeds, only a single form of GS (GSs) was detected. Upon seed germination, the GSs isoform was gradually replaced by cytosolic (GS1) and plastidic (GS2) isoforms. Light and nitrate decreased the levels of GS1. In contrast, the appearance of GS2 was greatly stimulated by light. Nitrate also had a positive effect, particularly in the light. Light and nitrate acted synergistically on the appearance of GS2. The GS2:GS1 ratio in cotyledons of 9-d-old seedlings ranged from about 2, in darkness and nitrate-deprivation conditions, to 16 under light and nitrate application. The possible physiological roles of the distinct GS isoforms appearing in the epigeal cotyledons of sunflower during germination, and their differential regulation by light and nitrate, are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198038
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A randomized multicentric study comparing alternating combination chemotherapy (VCMP/VBAP) and melphalan-prednisone in multiple myeloma (1990)
    Springer
    Annals of hematology 60 (1990), S. 319-322 
    Details
    ISSN: 1432-0584
    Keywords: Multiple myeloma ; Combination chemotherapy ; VCMP/VBAP ; MP treatment ; Survival
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Between January 1985 and December 1988, 386 patients with multiple myeloma were randomized to receive either MP or combination chemotherapy based on alternating cycles of VCMP and VBAP. The major prognostic parameters did not differ significantly between both treatment groups. A significantly higher proportion of objective responses was observed with combination chemotherapy as compared to MP (47.8 vs 32.2,P = 0.01). The median survival for all patients was 33.5 months. So far no significant differences were found when comparing the survival curves from both groups of patients. However, the median survival of MP-treated patients is 26.8 months, whereas the median survival of patients receiving VCMP/VBAP has not yet been reached. The definitive analysis must await the evaluation of all patients entered into the study and a longer follow-up time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01737844
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Nitrate and nitrite uptake and reduction by intact sunflower plants (1990)
    Springer
    Planta 182 (1990), S. 149-154 
    Details
    ISSN: 1432-2048
    Keywords: Helianthus ; Nitrate (reduction, uptake) ; Nitrite (reduction, uptake)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen-starved sunflower plants (Helianthus annuus L. cv. Peredovic) cannot absorb NO 3 − or NO 2 − upon initial exposure to these anions. Ability of the plants to take up NO 3 − and NO 2 − at high rates from the beginning was induced by a pretreatment with NO 3 − . Nitrite also acted as inducer of the NO 2 − -uptake system. The presence of cycloheximide during NO 3 − -pretreatment prevented the subsequent uptake of NO 3 − and NO 2 − , indicating that both uptake systems are synthesized de novo when plants are exposed to NO 3 − . Cycloheximide also suppressed nitrate-reductase (EC 1.6.6.1) and nitrite-reductase (EC 1.7.7.1) activities in the roots. The sulfhydryl-group reagent N-ethylmaleimide greatly inhibited the uptake of NO 3 − and NO 2 − . Likewise, N-ethylmaleimide promoted in vivo the inactivation of nitrate reductase without affecting nitrite-reductase activity. Rates of NO 3 − and NO 2 − uptake as a function of external anion concentration exhibited saturation kinetics. The calculated Km values for NO 3 − and NO 2 − uptake were 45 and 23 μM, respectively. Rates of NO 3 − uptake were four to six times higher than NO 3 − -reduction rates in roots. In contrast, NO 2 − -uptake rates, found to be very similar to NO 3 − -uptake rates, were much lower (about 30 times) than NO 2 − -reduction rates. Removal of oxygen from the external solution drastically suppressed NO 3 − and NO 2 − uptake without affecting their reduction. Uptake and reduction were also differentially affected by pH. The results demonstrate that uptake of NO 3 − and NO 2 − into sunflower plants is mediated by energy-dependent inducible-transport systems distinguishable from the respective enzymatic reducing systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239997
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Organic nitrogen content and nitrate and nitrite reductase activities in tritordeum and wheat grown under nitrate or ammonium (1991)
    Springer
    Plant and soil 135 (1991), S. 251-256 
    Details
    ISSN: 1573-5036
    Keywords: nitrate reductase ; nitrite reductase ; organic nitrogen ; tritordeum ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Tritordeum is a fertile amphiploid derived from durum wheat (Triticum turgidum L. conv. durum) × a wild barley (Hordeum chilense Roem. et Schultz.). The organic nitrogen content of tritordeum grain (34 mg g-1 DW) was significantly higher than that of its wheat parent (25 mg g-1 DW). Leaf and root nitrogen content became higher in tritordeum than in wheat after four weeks of growth, independently of the nitrogen source (either NO3 - or NH4 +). Under NO3 - nutrition, tritordeum generally exhibited higher levels of nitrate reductase (NR) activity than wheat. Nitrite reductase (NiR) levels were however lower in tritordeum than in its wheat parent. In NH4 +-grown plants, both NR and NiR activities progressively decreased in the two species, becoming imperceptible after 3 to 5 weeks of growth. Results indicate that, in addition to a higher rate of NO3 - reduction, other physiological factors must be responsible for the greater accumulation of organic nitrogen in tritordeum grain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010913
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    Paper (German National Licenses)
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