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  • 11
    Electronic Resource
    Electronic Resource
    Photoinhibition by visible and ultraviolet radiation in the red macroalga Porphyra umbilicalis grown in the laboratory (1999)
    Springer
    Plant ecology 145 (1999), S. 351-358 
    Details
    ISSN: 1573-5052
    Keywords: oxygen measurements ; PAM fluorescence ; photoinhibition ; Porphyra ; rhodophyta ; ultraviolet radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthetic oxygen production and PAM fluorescence measurements were used to follow photoinhibition in the red macroalga Porphyra umbilicalis. Exposure to simulated solar radiation caused inhibition of the effective photosynthetic quantum yield from which the thalli partially recovered in the shade in subsequent hours. There were no significant differences between samples exposed to unfiltered radiation and those exposed to radiation from which increasing portions of UV radiation had been removed indicating that the thalli are well adapted to current levels of solar PAR and UV radiation. This notion was supported by the finding of high concentrations of UV screening pigments which were even enhanced by exposure to increased UV radiation. However, when exposed to (only) UV radiation about 50% higher than that encountered by the organisms in their natural habitat, the photosynthetic yield decreased slowly and did not show any recovery even when the degree of inhibition did not exceed 10%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009833520770
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  • 12
    Electronic Resource
    Electronic Resource
    Optimized nitrate reductase assay predicts the rate of nitrate utilization in the halotolerant microalga Dunaliella viridis (1997)
    Springer
    Journal of applied phycology 9 (1997), S. 99-106 
    Details
    ISSN: 1573-5176
    Keywords: Nitrate reductase ; in situ enzymatic activity ; Dunaliella viridis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An in situ method for measuring nitrate reductase (NR) activity in Dunaliella viridis was optimized in terms of incubation time, concentration of KNO3, permeabilisers (1-propanol and toluene), pH, salinity, and reducing power (glucose and NADH). NR activity was measured by following nitrite production and was best assayed with 50 mM KNO3, 1.2 mM NADH, 5% 1-propanol (v/v), at pH 8.5. The estimated half-saturation constant (Ks) for KNO3 was 5 mM. Glucose had no effect as external reducing power source, and NADH concentrations 〉1.2 mM inhibited NR activity. Nitrite production was linear up to 20 min; longer incubation did not lead to higher nitrate reduction. The use of the optimized assay predicted the rate of NO 3 − removal from the external medium by D. viridis with high degree of precision.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007978512458
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  • 13
    Electronic Resource
    Electronic Resource
    Influence of subsidiary energy on growth ofDunaliella viridis Teodoresco: the role of extra energy in algal growth (1994)
    Springer
    Journal of applied phycology 6 (1994), S. 323-330 
    Details
    ISSN: 1573-5176
    Keywords: Dunaliella viridis ; subsidiary energy quantification ; growth ; carotenoids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An account is given of the influence of different levels of mechanical energy, in the form of bubbling, on the growth of the microalgaDunaliella viridis when other variables (e.g. temperature, nutrient supply, photon fluence) do not change. The extra energy was quantified accurately through the application of the classical equations of mass and energy conservation providing a method for the calculation of the energy efficiency of primary production related to the total energy input, in which photon fluence was found to be the most important. The specific growth rate (μ) of the population vs the input of auxiliary energy fits to a second order polynomial function with a maximum growth rate at 0.63 W m−2. The increase of maximal cell density follows a hyperbolic saturation kinetics, with saturation at those same values of extra energy. Both primary production and the efficiency of energy transformation inD. viridis vs the variation of total energy input fit to hyperbolic functions, reaching a maximum efficiency for primary production of 0.85%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02181946
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  • 14
    Electronic Resource
    Electronic Resource
    Cytotoxic Triterpene Glycosides from Far-Eastern Sea Cucumbers Belonging to the Genus Cucumaria (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2351-2356 
    Details
    ISSN: 0947-3440
    Keywords: Carbohydrates ; Cucumaria japonica ; Cucumaria miniata ; Sea cucumbers ; Cucumariosides ; Triterpene glycosides ; Antitumor activity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New cytotoxic triterpene oligoglycoside disulfates, cucumariosides A3 (1) and A6-2 (2), have been isolated from the sea cucumber Cucumaria japonica. The trisulfated cucumarioside A7-3 (4) was found to be the major component in the glycoside fraction of Cucumaria miniata. The structures were assigned on the basis of extensive spectral data (NMR and MS), selective solvolysis of desulfated derivative 3 and other chemical evidence. The presence or absence of a carbonyl group at C-16 of the aglycone and of sulfate groups at C-6 of the glucose and 3-O-methylglucose units are interpreted in terms of the functional evolution of sea cucumbers in order to improve their defensive system. Both (1) and (2) are cytotoxic in vitro at IC50 = 1 μg/ml against a selection of five human and mice tumoral cell lines.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971125
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