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  • 1980-1984  (3)
  • 1975-1979  (1)
  • 1935-1939
  • Life and Medical Sciences  (3)
  • Data transformation  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Data transformation as a scaling operation in ordination of plankton (1984)
    Springer
    Plant ecology 56 (1984), S. 147-160 
    Details
    ISSN: 1573-5052
    Keywords: Data transformation ; Ordination ; Phytoplankton ; Principal components analysis ; Scale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Data transformation is seen here as an aspect of scaling such that we are less interested in the quirks and properties of each transformation but are more concerned with the general scaling properties and trends of suites of transformations. Over two years of daily phytoplankton abundance data for 30 species from a temperate lake (Llyn Maelog, North Wales) were subjected to a series of scale-ordered transformations. Two major classes of transformation were systematically varied: binary and smoothing. Binary transformation scaled the cutoff threshold between ‘presence’ and ‘absence’ of a species to various levels of abundance. With successively smaller universes and smoothing windows and successive species exclusion, ordinations of sample dates revealed smaller scaled structures in the order: annual cycles of species turnover, seasonal areas of attraction and uniqueness of individual sample dates. Gradual increases in the length of the smoothing window resulted in gradual shifts in the positions of points in sample data ordination, but not necessarily in the species ordinations. Thus sample data structures are more stable with change in scale than are species data structures. These differences in stability are discussed in the context of filtering characteristics of data collection and data analysis. Transformations producing similar species statistics (means, variances and skews) did not generally give similar ordination results, while some transformations giving similar ordinations differed in species statistical parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00045222
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The migration of lymphocytes across specialized vascular endothelium: VIII. Physical and chemical conditions influencing the surface morphology of lymphocytes and their ability to enter lymph nodes (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 170 (1984), S. 377-390 
    Details
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The introductory review amplifies the finding that simply holding lymphocytes in vitro reversibly compromises their ability to enter lymph nodes from the blood, although entry into the spleen is unaffected. The differential migration of T and B lymphocytes from the blood, lymphocyte traffic in athymic rats, and the secretion of a sulphated glycoconjugate by high endothelial cells in lymph nodes are also discussed.Original data are presented concerning the effects of varying the conditions under which lymphocytes are held in vitro (time, temperature, medium, centrifugation) on their ability to enter lymph nodes and also on their surface morphology. In general, conditions that reduced the number of microvilli and induced surface blebbing also tended to affect the delicate function of crossing specialized vascular endothelium; but there was no simple relationship between morphology and migratory behavior. The localization of lymphocytes to the bone marrow was augmented by holding them in vitro, and this effect was greater after holding at room temperature (RT) than at 0°C, in contrast to impaired entry into lymph nodes. Small amounts of heparin (10 units) injected along with lymphocytes significantly reduced early localization in lymph nodes. These findings have practical implications for the design of lymphocyte traffic experiments and are relevant to the mechanism of lymphocyte attachment to vascular endothelium, since the well-known effect of trypsinizing lymphocytes can be reproduced by maintenance in vitro.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001700312
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Conditions controlling the proliferation of haemopoietic stem cells in vitro (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 91 (1977), S. 335-344 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A liquid culture system is described whereby proliferation of haemopoietic stem cells (CFU-S), production of granulocyte precursor cells (CFU-C), and extensive granulopoiesis can be maintained in vitro for several months. Such cultures consist of adherent and non-adherent populations of cells. The adherent population contains phagocytic mononuclear cells, “epithelial” cells, and “giant fat” cells. The latter appear to be particularly important for stem cell maintenance and furthermore there is a strong tendency for maturing granulocytes to selectively cluster in and around areas of “giant fat” cell aggregations. By “feeding” the cultures at weekly intervals, between 10 to 15 “population doublings” of functionally normal CFU-S regularly occurs. Increased “population doublings” may be obtained by feeding twice weekly. The cultures show initially extensive granulopoiesis followed, in a majority of cases, by an accumulation of blast cells. Eventually both blast cells and granulocytes decline and the cultures contain predominantly phagocytic mononuclear cells.Culturing at 33°C leads to the development of a more profuse growth of adherent cells and these cultures show better maintenance of stem cells and increased cell density.When tested for colony stimulating activity (CSA) the cultures were uniformly negative. Addition of exogenous CSA caused a rapid decline in stem cells, reduced granulopoiesis and an accumulation of phagocytic mononuclear cells.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040910303
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Clonal preadipocyte cell lines with different phenotypes derived from murine marrow stroma: Factors influencing growth and Adipogenesis in vitro (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 111 (1982), S. 177-186 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have isolated continuously growing cell lines derived from mouse bone marrow stroma. These cell lines were independently obtained, and though they showed morphologies ranging from the epithelioid to the fibroblastoid patterns, they all differentiated into adipocytes. Subclones obtained from two cell lines had a very high frequency (90-100%) of differentiation into adipocytes after two or three weeks of arrested growth. Though extensive accumulation of lipid often mechanically impaired mitosis, the cells committed to adipocytes did not suffer an irreversible loss of proliferative capacity. Adipogenesis was obtained in conditions similar to those required for fat cell formation in long-term bone marrow culture. The cell lines were found to be insensitive to insulin as a signal of adipocyte differentiation. The ultrastructural characteristics of the preadipocytes and fat cells are also similar to those of the fat cells developing in long-term bone marrow culture. As such, these cell lines should prove useful for analysing cell/cell interactions in haemopoiesis.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041110209
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    Paper (German National Licenses)
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