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  • shallow lakes  (4)
  • Artemisinin  (2)
  • 1990-1994  (6)
  • 1
    Electronic Resource
    Electronic Resource
    Progress in the research of artemisinin-related antimalarials: An update (1994)
    Springer
    Pharmacy world & science 16 (1994), S. 169-180 
    Details
    ISSN: 1573-739X
    Keywords: Antimalarials ; Artemisia annua L ; Artemisinin ; Biosynthesis ; Chemistry ; Clinical trials ; Pharmacology ; Phytochemistry ; Sesquiterpenes ; Toxicology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Artemisinin, a sesquiterpene lactone endoperoxide isolated fromArtemisia annua L., and a number of its semisynthetic derivatives have shown to possess antimalarial properties. They are all eflective againstPlasmodium parasites that are resistant to the newest and commonly used antimalarial drugs. This article gives a survey of the literature dealing with artemisinin-relaled antimalarial issues that have appeared from the end of 1989 up to the beginning of 1994. A broad range of medical and pharmaceutical disciplines is covered, including phytochemical aspects like the selection of high-producing plants, analytical procedures, and plant biotechnology. Furthermore, the organic synthesis of artemisinin derivatives is discussed, as well as their mechanism of action and antimalarial activity, metabolism and pharmacokinetics, clinical studies, sideeffects and toxicology, and biological activities other than antimalarial activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01872865
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Artemisia annua L.: a source of novel antimalarial drugs (1990)
    Springer
    Pharmacy world & science 12 (1990), S. 169-181 
    Details
    ISSN: 1573-739X
    Keywords: Artemisia annua L. ; Artemisinin ; Biosynthesis ; Chemistry, analytical ; Clinical trials ; Pharmacology ; Sesquiterpene lactones ; Structure—activity relationship
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Artemisia annua L. contains artemisinin, an endoperoxide sesquiterpene lactone, mainly in its leaves and inflorescences. This compound and a series of derivatives have attracted attention because of their potential value as antimalarial drugs. In this review a survey of the currently available literature data is given. It includes phytochemical aspects, such as constituents ofA. annua, the artemisinin content during the development of the plant and its biosynthesis, isolation, analysis and stability. Total chemical synthesis of artemisinin is referred to, as well as structure—activity relationships of derivatives and simplified analogues. Pharmacological studies are summarized, including the mechanism of action, interaction of the antimalarial activity with other drugs, possible occurrence of resistance to artemisinin, clinical results, toxicological aspects, metabolism and pharmacokinetics. Finally, plant cell biotechnologyy is mentioned as a possible means to obtain plants and cell cultures with higher artemisinin contents, allowing an industrial production of pharmaceuticals containing this novel drug.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01980041
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Coupling of phytoplankton and detritus in a shallow, eutrophic lake (Lake Loosdrecht, The Netherlands) (1992)
    Springer
    Hydrobiologia 233 (1992), S. 51-59 
    Details
    ISSN: 1573-5117
    Keywords: phytoplankton ; Oscillatoria limnetica ; Prochlorothrix hollandica ; detritus ; shallow lakes ; lake restoration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An oscillating steady state is described of phytoplankton, dominated by Prochlorothrix hollandica and Oscillatoria limnetica, and sestonic detritus in shallow, eutrophic Lake Loosdrecht (The Netherlands). A steady-state model for the coupling of the phytoplankton and detritus is discussed in relation to field and experimental data on phytoplankton growth and decomposition. According to model predictions, the phytoplankton to detritus ratio decreases hyperbolically at increasing phytoplankton growth rate and is independent of a lake's trophic state. The seston in L. Loosdrecht contains more detritus than phytoplankton as will apply to many other lakes. The model provides a basis for estimating the loss rate of the detritus, including decomposition, sedimentation and hydraulic loss. In a shallow lake like L. Loosdrecht detritus will continue to influence the water quality for years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00016095
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Dynamics of phytoplankton detritus in a shallow, eutrophic lake (Lake Loosdrecht, The Netherlands) (1992)
    Springer
    Hydrobiologia 233 (1992), S. 61-67 
    Details
    ISSN: 1573-5117
    Keywords: phytoplankton ; epipelon ; Oscillatoria limnetica ; detritus ; shallow lakes ; lake restoration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A study was made of the mortality and aerobic decomposition of light- and phosphorus-limited cultures of Oscillatoria limnetica, a dominant phytoplankton species in shallow, eutrophic Lake Loosdrecht (The Netherlands). When placed in the dark at 20 °C, most cells died and lysed within twelve days. The labile organic matter was completely decomposed within three weeks. Absorbance spectra indicated that blue green algae may contributed significantly to the refractory dissolved substances in the lake. Refractory particulate matter constituted from 7 to 24% of the biomass of O. limnetica, depending on the growth rate before incubation in the dark. The decomposition rate of this fraction was 0.005 d−1. On a basis of a steady-state model of the dynamics of phytoplankton detritus, the areal organic dry weight concentration of the detritus in the lake is ca. 60 g m−2. This means the quantities of detritus in the seston and epipelon are about equal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00016096
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  • 5
    Electronic Resource
    Electronic Resource
    Characterization of the light field in laboratory scale enclosures of eutrophic lake water (Lake Loosdrecht, The Netherlands) (1992)
    Springer
    Hydrobiologia 238 (1992), S. 99-109 
    Details
    ISSN: 1573-5117
    Keywords: laboratory scale enclosure ; underwater light field ; shallow lakes ; phytoplankton ; cyanobacteria ; spectral light distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Light conditions in laboratory scale enclosures (LSE) of shallow, eutrophic Lake Loosdrecht (The Netherlands), including a method for simulating a ‘natural’ incident light course, are described. Total PAR (400–700 nm) and spectral irradiance distribution were measured at sestonic chlorophyll a and dry weight concentrations ≥ 100 mg m−3 and 16 g m−3, respectively. Phytoplankton was dominated by Oscillatoria spp. The euphotic depth (Z eu) was 0.7–1.0 m. Shortly after filling the LSE with lake water, diffuse attenuation coefficients ranged from 14 m−1 for blue to 5 m−1 for red light. Around Z eu, attenuation in the blue region was markedly lower and irradiance reflectance (R) continued to increase; these anomalies were caused by lateral incident light from the LSE's waterbath. Spectrophotometry indicated that absorption was mainly by particles, but dissolved humic substances (gilvin) were also important. The particles were likely to be dominated by detritus absorbing more blue relative to red light. Subsurface R in lake water in the LSE had a maximum around 705 nm and low values in the blue band, but was lower than that previously reported for measurements in situ. Wash-out of detritus, presumably both dissolved and particulate fractions, by flow-through with synthetic medium, greatly affected the spectral reflectance measured outside the LSE. The maximum value of R decreased from 0.022 to 0.009, and the peak shifted to 550 nm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00048778
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  • 6
    Electronic Resource
    Electronic Resource
    The ‘true’ growth efficiency of phytoplankton as influenced by light attenuation and insolation: implications of the photosynthesis-irradiance relationship (1992)
    Springer
    Hydrobiologia 238 (1992), S. 169-176 
    Details
    ISSN: 1573-5117
    Keywords: growth efficiency ; areal quantum efficiency ; light attenuation ; Oscillatoria limnetica ; shallow lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ‘true’ growth efficiency (c) relates the light energy absorbed by phytoplankton to the production of biomass corrected for constant energy requirement of maintenance. Continuous culture studies have shown that, at constant incident irradiance, the value of c for both prokaryotic and eukaryotic species is constant. Culture data for the relevant conditions of incident light may be used for directly estimating the growth rate from daily insolation of optically deep, fully mixed lakes, when the light absorption by the phytoplankton can be established. In order to examine the influence of vertical light attenuation and daily insolation on c, computations were made on a basis of a photosynthesis-irradiance curve of light-limited Oscillatoria limnetica. For steady state growth, the ‘true’ growth efficiency is linearly related to the areal quantum efficiency of photosynthesis (ϕ a ). The computations showed that ϕ a remains constant at fluctuating vertical light attenuation, no matter whether the concentration of tripton or phytoplankton changes. The effect of insolation is great: ϕ a is 0.108 mol O2/E at very low light, but only 0.014 mol O2/E at 400 W m−2 subsurface downward irradiance. The results imply that a c-value obtained from cultures for summer averaged insolation must be corrected: between cloudy and clear days the value may vary by a factor of 2. The ‘true’ growth efficiency for cultures will decrease by about 10% when the same daily irradiation is dosed sinusoidally instead of constantly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00048785
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    Paper (German National Licenses)
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