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  • 1980-1984  (3)
  • 1935-1939
  • Cell & Developmental Biology  (2)
  • Correlation matrix  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Plant ecology 51 (1983), S. 141-155 
    ISSN: 1573-5052
    Keywords: Correlation matrix ; Dispersion matrix ; Forest model ; Hierarchical structure ; Ordination ; Principal components analysis ; Simulation ; Succession
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A model of a 1/12th ha forest stand, FORET, generated 10 000 years of simulated species succession. Approximately the first third of these results were analyzed by principal component analysis as if they were collected field data to give the trajectory of the community particle in a collapsed species space. The ordination axis orientation was performed on a dispersion matrix and correlation matrix between species. In both cases, however, the eigen vectors were applied to the data matrix which had not been transformed to unit species variance. This facilitated comparison of species dispersion and correlation structure; it emerged they were very different. Correlation structure gave large weights to understory species while dispersion emphasized the dominant overstory species. This implies a decomposition of simulated stand behavior into overstory and understory, even though such decomposition was not formally built into the model. This decomposition would seem to pertain to real vegetation. Principal component analysis was able to express insightful differences between data structure with and without the unit variance transformation implicit in the correlation matrix. This flexibility of the ordination method proved valuable in uncovering unsuspected ordering principles in the model. Complex simulated data allow the ordination technique to demonstrate its capacity to generate new hypotheses, which hypotheses can then be simply validated by a return to the structure of the model but with the hindsight of the analysis. The generation of new hypotheses is not possible if the simulation is of a simple coenocline; on the other hand, ordination of test field data does not allow the simple validation of new hypotheses, for in the field there is not a defined algorithm to which the researcher can return.
    Type of Medium: Electronic Resource
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  • 2
    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
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 111 (1982), S. 177-186 
    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
    Library Location Call Number Volume/Issue/Year Availability
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