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  • 1
    Electronic Resource
    Electronic Resource
    Historical changes in sediments of Pyramid Lake, Nevada, USA: consequences of changes in the water balance of a terminal desert lake (1994)
    Springer
    Journal of paleolimnology 12 (1994), S. 87-101 
    Details
    ISSN: 1573-0417
    Keywords: Great Basin ; climatic variations ; productivity ; organic matter ; nitrogen ; phosphorus ; hardwater lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Sediment cores from the shallow and deep basins of Pyramid Lake, Nevada, revealed variations in composition with depth reflecting changes in lake level, river inflow, and lake productivity. Recent sediments from the period of historical record indicate: (1) CaCO3 and organic content of sediment in the shallow basin decrease at lower lake level, (2) CaCO3 content of deep basin sediments increases when lake level decreases rapidly, and (3) the inorganic P content of sediments increases with decreasing lake volume. Variations in sediment composition also indicate several periods for which productivity in Pyramid Lake may have been elevated over the past 1000 years. Our data provide strong evidence for increased productivity during the first half of the 20th Century, although the typical pattern for cultural eutrophication was not observed. The organic content of sediments also suggests periods of increased productivity in the lake prior to the discovery and development of the region by white settlers. Indeed, a broad peak in organic fractions during the 1800's originates as an increase starting around 1600. However, periods of changing organic content of sediments also correspond to periods when inflow to the lake was probably at extremes (e.g. drought or flood) indicating that fluctuations in river inflow may be an important factor affecting sediment composition in Pyramid Lake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00678089
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  • 2
    Electronic Resource
    Electronic Resource
    Nutrient cycling and productivity in a desert saline lake: observations from a dry, low-productivity year (1992)
    Springer
    Hydrobiologia 246 (1992), S. 213-229 
    Details
    ISSN: 1573-5117
    Keywords: Nutrient cycling ; productivity ; internal loading ; seasonal variations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seasonal variability of nutrients and productivity were examined in Pyramid Lake, a hyposaline, N-deficient, terminal desert lake, during a dry period. River inflow and N-fixation during 1990 were minimal allowing internal nutrient cycling to be more closely studied. Nutrient cycling was strongly affected by seasonal thermal stratification that was typical for a warm monomictic lake. Concentrations of nitrate, phosphate, and silicate in surface waters were highest during winter mixing and decreased rapidly in the spring due to a diatom bloom. Maximum average chlorophyll concentration in surface waters was 2.7 ± 1.2 µg 1−1 and occurred in April while surface nutrients were being depleted. In contrast to chlorophyll, maximum particulate carbon in surface waters occurred in July–August when areal productivity was highest (367–398 mg C m−2 day−1). Concurrent with spring nutrient depletion in surface waters was increasing N-deficiency in the plankton. After the spring bloom dissipated in May, particulate matter (POM) became increasingly N-deficient reaching maximum elemental C : N of 〉 18 during summer-fall. Profiles of the C : N ratio of POM were nearly constant with depth for individual sampling dates suggesting that the residence time of POM in the water column was short (〈 1 month). While surface waters were nutrient depleted during summer stratification, nutrient concentrations of bottom waters progressively increased, presumably through the oxidation of POM sinking to the bottom (103 m). Converting the rate of oxygen depletion in bottom waters to carbon equivalents of POM suggests that 42 % of mean annual phytoplankton production in overlying waters during 1990 was mineralized in bottom waters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00005699
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  • 3
    Electronic Resource
    Electronic Resource
    Human prostate cancer model: Roles of growth factors and extracellular matrices (1992)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 50 (1992), S. 99-105 
    Details
    ISSN: 0730-2312
    Keywords: extracellular matrices (ECMs) ; bFGF ; NGF ; HGF and KGF ; growth factors (GFs) ; human prostate cancer model ; prostate cancer-bone interaction ; stromal-epithelial interaction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A human prostate cancer model was established by inoculating a prostate specific antigen (PSA)-producing LNCaP cell line with either prostate or bone fibroblasts. Alternatively, this human prostate cancer model can also be established by inoculating LNCaP cell with growth factor(s) (GFs) and extracellular matrix (ECM) immobilized on Gelfoam®. The resulting LNCaP tumors were used to evaluate PSA production and excretion athymic hosts. This model was also employed to examine the biochemical nature of mesenchymal cell-derived growth-promoting protein(s) and to assess the efficacy of potential chemotherapeutic agents. Because of the propensity of human prostate cancer to metastasize to the bone, this study defined a 1.0 M NaCI-eluted fraction, MS1, from the conditioned medium of a bone stromal cell line (MS) by heparin-affinity column chromatography. The growth-promoting activity was assayed both in vivo (e.g., tumor formation) and in vitro (e.g., soft agar colony formation). We found that the growth-promoting activity was trypsin-and heat-sensitive, and partially degraded by acid and dithiothreitol. Immunochemical studies indicated that the polyclonal antibody raised against MS1 blocked the growth-promoting effect elicited by the bone-conditioned media. This growth-promoting factor was found to be immunochemically dissimilar to KGF, HGF, and bFGF. However, addition of bFGF, HGF and NGF, but not a FGF, TGFβ, IGF1, IGF2, PDGF, EGF, TGFα and KGF, stimulated anchorage-independent growth of prostate cells, a condition closely parallel to tumor formation in vivo. We found that the MS1 fraction also contained fibronectin and tenascin but not laminin or collagen IV. None of the ECM proteins induced soft agar colony formation by normal prostate epithelial cells. Therefore, it is possible that the ECM protein(s) may potentiate the tumor-inducing activity of locally produced GFs. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240501222
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    Paper (German National Licenses)
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