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  • laboratory scale enclosure  (4)
  • Pharmacology  (3)
  • lake restoration  (3)
  • 1
    Electronic Resource
    Electronic Resource
    The eutrophic Loosdrecht Lakes: Current ecological research and restoration perspectives (1986)
    Springer
    Aquatic ecology 20 (1986), S. 61-75 
    Details
    ISSN: 1573-5125
    Keywords: eutrophication ; lake restoration ; blue-green algae ; zooplankton ; seston ; epipelon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Features of the Loodsrecht Lakes, with emphasis on the main lake, are discussed with reference to restoration. Characteristics of the present situation are: (1) very low water transparency-Secchi-disc readings around 0.3 m occur in all seasons; (2) relatively small seasonal changes in sestonic matter; (3) important input of resuspended particles into the seston; (4) predominance of filamentous blue-green algae for most of the year; (5) relative scarcity of crustacean zooplankton, while rotifers are abundant; (6) poor development of littoral communities, and absence of benthic producers. The blue-green algae maintain high population density at very low growth rates: rates of loss are low. The zooplankton grazing rate is low due to inefficient filtering, but predation of larger crustaceans by fish may also be important. Studies on epipelon indicated that loss by deposition may be largely compensated by resuspension. Starting in 1984, the external phosphorus loading was markedly reduced. Results for 1984 and 1985 indicate that complementary measures are needed in order to improve water quality. Action should be directed towards increasing the phytoplankton turnover rates. Accelerated specific growth rate can be expected to accompany lower biomass, more successful competition by other algal groups, and enhancement of grazing pressure. Considering the shallowness of the system, promotion of littoral development and return of submerged vegetation may be important in establishing a new equilibrium of the system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02291151
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  • 2
    Electronic Resource
    Electronic Resource
    Phosphate uptake capacity of summer phytoplankton of the Loosdrecht Lakes in relation to phosphorus loading and irradiance (1986)
    Springer
    Aquatic ecology 20 (1986), S. 101-107 
    Details
    ISSN: 1573-5125
    Keywords: phytoplankton ; laboratory scale enclosure ; phosphorus loading ; phosphate uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Summer populations of the phytoplankton of the Loosdrecht Lakes were enclosed in laboratory scale enclosures (LSE), supplied with 7.5 μg P.l−1.d−1 and 105 μg P.l−1.d−1, respectively. The maximum initial phosphate uptake rate (Vm) was related to irradiance and primary production. At phosphate uptake saturating light-irradiance Vm values up to 4 times the Vm values in the dark were measured. The phosphate uptake capacity per unit dry weight remained more or less constant throughout the experiments in the LSE receiving the lower amount of phosphorus, and declined in the LSE receiving the higher amount of phosphorus. Within the range of Vm values measured (〈10 μg P.mg DW−1.h−1 or 1,3 μg P. μg chla −1.h−1), the growth rate of the phytoplankton was not influenced by alterations in phosphorus availability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02291155
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  • 3
    Electronic Resource
    Electronic Resource
    A comparison of primary production measurements using two laboratory systems with differences in light quality (1986)
    Springer
    Aquatic ecology 20 (1986), S. 93-99 
    Details
    ISSN: 1573-5125
    Keywords: primary production ; oxygen technique ; light quality ; incubator ; laboratory scale enclosure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Primary production measurements were carried out simultaneously, using two laboratory systems with different light conditions: (1) a'classical' incubator and (2) a Laboratory Scale Enclosure. The model used for calculating primary production (STEELE, 1965) does not correct for spectral changes caused by high phytoplankton biomass. In the incubator, light of almost all wavelengths decreased more or less according to the attenuation of total PhAR in water. In the LSE, high absorption was found of the blue light and some of the red light, which was due to the high sestonic concentration. The Steele function provided a good fit for both sets of data. The depth integrated gross production values derived from the simultaneous measurements were not significantly different.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02291154
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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    Traditional Chinese herbal medicine (1995)
    Springer
    Pharmacy world & science 17 (1995), S. 103-112 
    Details
    ISSN: 1573-739X
    Keywords: Books ; Drug screening ; Drugs, Chinese herbal ; Education ; History of medicine ; Medicine, Chinese traditional ; Pharmacology ; Quality control ; Research
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Herbal medicine, acupuncture and moxibustion, and massage are the three major constituent parts of traditional Chinese medicine. Although acupuncture is well known in many Western countries, Chinese herbal medicine, the most important part of traditional Chinese medicine, is less well known in the West. This article gives a brief introduction to the written history, theory, and teaching of Chinese herbal medicine in China. It also describes modern scientific research into and the quality control of Chinese herbal medicines in China. Some examples of how new drugs derived from Chinese herbs have been developed on the basis of traditional therapeutic experience are presented. Finally, the situation of Chinese herbal medicine in the West is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01872386
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Interspecific variation in pigmentation: implications for production estimates for shallow eutrophic lakes using an incubator (1992)
    Springer
    Hydrobiologia 238 (1992), S. 197-202 
    Details
    ISSN: 1573-5117
    Keywords: primary production ; spectral light distribution ; incubator ; laboratory scale enclosure ; Oscillatoria limnetica ; Prochlorothrix hollandica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In shallow, eutrophic Lake Loosdrecht, light attenuation and spectral changes with depth are pronounced due to high concentration of algae and tripton. Calculations of integrated daily primary production have been based on the photosynthesis-irradiance relationship (P/E-curve) obtained with the incubator technique. The suitability of this technique for estimating primary production in such a turbid lake was investigated by comparing P/E-curves for two differently pigmented algae, Oscillatoria limnetica and Prochlorothrix hollandica, in two laboratory systems differing in light regime. System (1) consisted of an incubator filled with tapwater, and system (2) was an algal culture in a laboratory scale enclosure (LSE). For O. limnetica the P/E-curves were identical. The P/E-curves for P. hollandica diverged considerably: the photosynthetic efficiency in the LSE (0.19 mg O2 (mg Chl)−1 h−1 (W m−2)−1 was about half of that obtained in the incubator (0.35 mg O2 (mg Chl)−1 h−1 (W m−2)−1. These results were explained by the interspecific variation in pigmentation. The photosynthetic efficiency of P. hollandica changed due to the dependence on the chlorophyll specific absorption for the whole photosynthetic waveband on the spectral light distribution, which for O. limnetica was approximately the same in the two light regimes. Column-integrated primary production computed with the photosynthetic characteristics of P. hollandica obtained in LSE, was 10–30% lower than the production based on incubator data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00048789
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  • 8
    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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  • 9
    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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  • 10
    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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