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  • Clinical trials  (2)
  • Loosdrecht lakes  (2)
  • 1990-1994  (4)
  • 1920-1924
  • 1
    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
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pharmacy world & science 12 (1990), S. 169-181 
    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
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 191 (1990), S. 241-248 
    ISSN: 1573-5117
    Keywords: Loosdrecht lakes ; eutrophication ; Prochlorothrix hollandica ; growth kinetics of algae ; continuous cultures ; light attenuation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytoplankton growth in the shallow, turbid Lake Loosdrecht (The Netherlands) is importantly influenced by light availability, and thus the concentrations of the various light-attenuating materials. The system is highly eutrophic and supports an algal biomass of ca. 160 mg Chl m−3. A model is proposed here which predicts algal growth in the lake as a function of the light received and subsequent attenuation in the water column by phytoplankton, tripton and background colour. The model is based on an energy balance which relates growth rate to the ‘true’ growth yield on light energy and the energy demand for cell maintenance. The coefficients for energy conversion (Y = 0.002 gDW kJ−1) and cell maintenance (µe = 0.031 day−1) were determined from steady state growth kinetics of Prochlorothrix hollandica in light-limited laboratory flow systems with the same depth as the lake and receiving summer average conditions of irradiance. Light attenuation by phytoplankton and tripton were quantified using specific attenuation coefficients: 0.011 m2 mg−1 Chl for the phytoplankton and 0.23 m2 g−1 DW for tripton. The growth studies demonstrated that Lake Loosdrecht can support a much higher algal biomass in the absence of non-algal particulate matter. The proposed model is used to predict chlorophyll a concentrations in dependence on growth rate and levels of tripton. Since approximately 75% of the sestonic dry weight in Lake Loosdrecht may be attributed to tripton, it is concluded that the algal biomass is markedly lowered by the abundance of tripton in the water column. A knowledge of the sources and fate of tripton in the lake is thus of fundamental importance in modelling phytoplankton dynamics.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-5117
    Keywords: Loosdrecht lakes ; eutrophication ; underwater light ; resuspension ; wind effect ; Prochlorothrix hollandica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Loosdrecht (The Netherlands) is shallow, highly eutrophic and subject to frequent wind-induced resuspension of settled algae and detritus. The summer phytoplankton consists of filamentous prokaryotic species. Chlorophyll a levels are rather stable over the summer at a concentration of ca. 160 mg m−3; losses due to grazing and sinking are small. Epipelic chlorophyll a concentrations range from 0 to 250, but ca. 50 mg m−2 is typical. In situ rates of change of chlorophyll a in the water column were related to specific growth rates predicted by a model for light-limited growth. In the model, incident light is partitioned among algae, tripton and background colour, to determine the light available for algal growth and cell maintenance. Model coefficients were derived primarily from laboratory studies of the growth of Prochlorothrix hollandica, an abundant species in the lake in summer. Presuming constant rates of loss due to grazing and sinking, for summers 1985 and 1986 some 56% of the variation in the chlorophyll a in the lake water was explained by change in light conditions alone and 77% by light and wind-driven resuspension of epipelic chlorophyll a together. These factors had little influence on the phytoplankton biomass in 1983 and 1984; other environmental conditions, e.g. phosphorus availability, may have been important. Also, the laboratory-derived growth kinetics of P. hollandica may not have been equally suitable for modelling in the four summers.
    Type of Medium: Electronic Resource
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