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  • 1
    Electronic Resource
    Electronic Resource
    Downstream effects of impoundments on the water chemistry of the Buffalo River (Eastern Cape), South Africa (1990)
    Springer
    Hydrobiologia 202 (1990), S. 71-83 
    Details
    ISSN: 1573-5117
    Keywords: reservoir impact ; serial discontinuity ; water quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The downstream effects of impoundments on the chemistry of pristine and polluted stretches of the Buffalo River were investigated in the context of the Serial Discontinuity Concept (Ward & Stanford, 1983). Impoundments which received water from a near-pristine upper catchment caused alterations of the water quality which were consistent with the Serial Discontinuity Concept, and recovery to riverine conditions was within 2.6 to 18.4 km of the dam, depending on flow. Impoundments which received agricultural runoff and urban effluents generally caused an improvement in the water quality of the downstream reaches (with the exception of nitrate concentrations, which were higher in the tailwaters compared to inflowing water). Impoundments with polluted inflows therefore usually ‘reset’ the river towards its natural condition, rather than acting as perturbations. This represents a reversal of the Serial Discontinuity Concept described for pristine rivers. The downstream effects of impoundments on water chemistry therefore depend on the relative impact of other catchment perturbations. These disturbances become more severe during low flow, and it is during this time that the impoundments have the greatest effect on the river.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02208128
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  • 2
    Electronic Resource
    Electronic Resource
    Downstream effects of impoundments on the water chemistry of the Buffalo River (Eastern Cape), South Africa (1990)
    Springer
    Hydrobiologia 202 (1990), S. 71-83 
    Details
    ISSN: 1573-5117
    Keywords: reservoir impact ; serial discontinuity ; water quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The downstream effects of impoundments on the chemistry of pristine and polluted stretches of the Buffalo River were investigated in the context of the Serial Discontinuity Concept (Ward & Stanford, 1983). Impoundments which received water from a near-pristine upper catchment caused alterations of the water quality which were consistent with the Serial Discontinuity Concept, and recovery to riverine conditions was within 2.6 to 18.4 km of the dam, depending on flow. Impoundments which received agricultural runoff and urban effluents generally caused an improvement in the water quality of the downstream reaches (with the exception of nitrate concentrations, which were higher in the tailwaters compared to inflowing water). Impoundments with polluted inflows therefore usually ‘reset’ the river towards its natural condition, rather than acting as perturbations. This represents a reversal of the Serial Discontinuity Concept described for pristine rivers. The downstream effects of impoundments on water chemistry therefore depend on the relative impact of other catchment perturbations. These disturbances become more severe during low flow, and it is during this time that the impoundments have the greatest effect on the river.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027093
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  • 3
    Electronic Resource
    Electronic Resource
    An assessment of macroinvertebrate functional feeding groups as water quality indicators in the Buffalo River, eastern Cape Province, South Africa (1996)
    Springer
    Hydrobiologia 318 (1996), S. 153-164 
    Details
    ISSN: 1573-5117
    Keywords: macroinvertebrates ; water quality ; bio-indicators ; functional feeding groups
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aim of this paper was to investigate the potential for using functional feeding groups (FFGs) as indicators of water quality conditions in rivers, using the Buffalo River, South Africa, as a specific example. Multivariate classification and ordination techniques were used to investigate species and FFG distributions in relation to a number of physico-chemical variables at 16 sites from the headwaters to the estuary of the Buffalo River. Two-way indicator species analysis (TWINSPAN) of species composition ranked most of the sites sequentially down the river, irrespective of water quality conditions. Ordination of FFGs from a set of riffle samples collected in mid-late summer showed only weak relationships between FFG distribution and water quality changes, except where variables changed sequentially down the river (e.g. pH and temperature). Individual species responses to water quality gradients were examined for nine riffle-dwelling species representing diverse FFGs. Following correspondence analysis of a matrix of environmental variables and species frequencies, some species showed strong associations with defined ranges of some variables. In particular, Adenophlebia auriculata (Leptophlebiidae, Ephemeroptera) from the headwater sampling site, was associated with low pH and low temperature. Simulium damnosum occurred under conditions of high turbidity, while Afronurus harrisoni was found under high concentrations of potassium, ammonium and nitrite ions. We conclude that although there was a distinct headwaters fauna in the Buffalo River, and sequential downstream changes in species composition, most FFGs (apart from shredders) were represented down the whole length of the river. FFG classifications are therefore unlikely to provide useful indications of water quality conditions in the Buffalo River. Using a categorical approach to classifying water quality variables, and by applying correspondence analysis to the resulting matrix, we recognised nine species that could be used to define water quality. These indicator species can be used to define tolerance ranges of the fauna for water quality conditions in different parts of the Buffalo river.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00016677
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  • 4
    Electronic Resource
    Electronic Resource
    IL-3 and ribavirin induce differentiation and growth suppression during long-term treatment of a megakaryocytic leukemia cell line (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 165 (1995), S. 530-537 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Differentiation of the megakaryocytic leukemia cells, CMK, was induced by long-term (12 day) treatment with the combination of IL-3 and the nucleoside analogue ribavirin (RV), which reduces cellular GTP levels. In a previous report we demonstrated the induction of early messages and antigens, as well as the formation of giant polyploid cells in the cultures (Majumdar et al., 1994, J. Cell. Physiol., 160:29-39). Here we show high level induction of messages for the late markers, Platelet Factor 4, GMP140 (P-Selectin), thrombospondin, and beta thromboglobulin. The induced cells are also positive for these antigens by immunocytochemical analysis. The high level message induction resulted from synergy between the inducers. Pretreatment of the cells with IL-3 could accelerate the rise in message seen with the inducer combination. The increase in differentiation markers was accompanied by a reduction of the proliferative capacity of the cells. Riboguanosine, which has anti differentiation activity, blocked the induction of early and late antigens by the inducer combination, and also by IL-3 acting alone, but did not block the reduction in proliferative competence. In this model of megakaryocytic differentiation IL-3 treatment yields and initial stimulation of growth followed by growth supperssion, and is the principal driver of the differentiation process. RV functions primarily as a stimulator of message and protein expression in synergy with IL-3. © 1995 Wiley-Liss Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041650311
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  • 5
    Electronic Resource
    Electronic Resource
    IL-3 and ribavirin induce high level expression of megakaryocytic markers and messages during long-term treatment of a megakaryocytic leukemia cell line (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 160 (1994), S. 29-39 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Megakaryocyte differentiation is a lengthy process with cells moving through a continuum delineated by the sequential expression of specific gene products. The limited number of primary cells available from marrow for analysis has brought attention to some leukemic cell lines which show enhanced megakaryocyte marker expression following incubation with inducing agents, the most common of which is phorbol myristate acetate (PMA). We developed an alternative induction protocol for the megakaryocytic leukemic cell line CMK, which involved incubation of the cells with IL-3 and the nucleoside analog, ribavirin, for 1-2 weeks. This treatment was neither toxic nor cytostatic and yielded increased levels of the surface glycoproteins GPIIb/IIIA and GPIb-IX. Levels of some megakaryocytic messages (GPIIIa, GPIX) showed a marked rise by 12 days of incubation in the inducer combination. This was due to a synergistic interaction between IL-3 and ribavirin which influenced both transcriptional and posttranscriptional events. Light and electron microscopy demonstrated the presence of large polyploid cells, with morphological features similar to those of megakaryocytes, in the induced cultures. Analysis of the heterogeneity of response in the cell population to the induction regimen after several days of treatment suggested that cells which failed to display surface markers had been stimulated by the inducers but did not have sufficient time to complete expression of that marker. The results were consistent with the view that the cells in the starting population were distributed along a temporal expression pathway, and those which were first to express the earliest marker would also lead in the expression of a later marker. The order of expression was the same as that during normal megakaryocyte development. © 1994 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041600105
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  • 6
    Electronic Resource
    Electronic Resource
    Basic fibroblast growth factor and epidermal growth factor downmodulate the growth of hematopoietic cells in long-term stromal cultures (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 165 (1995), S. 386-397 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The bone marrow microenvironment consists of stromal cells and extracellular matrix components which act in concert to regulate the growth and differentiation of hematopoietic stem cells. There is little understanding of the mechanisms which modulate the regulatory role of stromal cells. This study examined the hypothesis that mesenchymal growth factors such as basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF) modulate stromal cell activities and thereby influence the course of hematopoiesis. Both bFGF and EGF were potent mitogens for marrow stroma. However, both factors proved to be inhibitory to hematopoiesis in primary log-term marrow cultures. Inhibition was also observed when hematopoietic cells and bFGF or EGF were added to subconfluent irradiated stromal layers, demonstrating that the decline of hematopoiesis was not due to overgrowth of the stromal layer. Loss of hematopoietic support in bFGF and EGF was dose-dependent. Removal of bFGF and EGF permitted stromal layers to regain their normal capacity to support hematopoiesis. In stroma-free long-term cultures, neither factor affected CFU-GM expansion. Basic FGF slightly enhanced granulocyte-macrophage colony forming unit (CFU-GM) cloning efficiency in short-term agarose culture. Basic FGF did not reduce the levels of interleukin-6 (IL-6), GM-CSF, or G-CSF released by steady state or IL-1-stimulated stroma. Similarly, the constitutive levels of steel factor (SF) mRNA and protein were not affected by bFGF. Basic FGF did not alter the level of TGF-β1 in stromal cultures. We conclude that bFGF and EGF can act as indirect negative modulators of hematopoietic growth in stromal cultures. The actual mediators of regulation, whether bound or soluble, remain to be identified. © 1995 Wiley-Liss, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041650220
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