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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Annals of hematology 49 (1984), S. 427-439 
    ISSN: 1432-0584
    Keywords: Hematopoiesis ; Stem cells ; Mathematical model ; Hypoxia ; Posthypoxia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A previously described mathematical model of the hematopoietic stem cell system has been extended to permit a detailed understanding of the data during and after hypoxia. The model includes stem cells, erythroid and granuloid progenitors and precursors. Concerning the intramedullary feedback mechanisms two basic assumptions are made: 1) The fraction “a” of CFU-S in active cell cycle is regulated. Reduced cell densities of CFU-S, progenitors or precursors lead to an accelerated stem cell cycling. Enlarged cell densities suppress cycling. 2) The self renewal probability “p” of CFU-S is also regulated. The normal steady state is described by p=0.5, indicating that on statistical average each dividing mother stem cell is replaced by one daughter stem cell, while the second differentiates. Diminished cell densities of CFU-S or enlarged densities of progenitors and precursors induce a more intensive self renewal (p〉0.5), such that the stem cell number increases. The self renewal probability declines (p〈0.5) if too many CFU-S or too few progenitors and precursors are present. The model reproduces bone marrow data for CFU-S, BFU-E, CFU-C, CFU-E, 59 Fe-uptake and nucleated cells in hypoxia and posthypoxia. Although the ratio of differentiation into the erythroid and granuloid cell lines is kept constant in the model, a changing ratio of CFU-E and CFU-C results. The model suggests that stem cells and progenitor cells are regulated by a regulatory interference of erythropoiesis and granulopoiesis.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 103 (1980), S. 355-362 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The numbers of CFU-S which developed in spleen colonies were measured 11 days after injection of irradiated mice with marrow from normal mice or mice which had been treated in one of a variety of ways. The broad spread of CFU-S numbers, seen by other authors, in colonies derived from normal marrow was confirmed. However, the range and distribution of CFU-S per colony was generally different in colonies derived from the marrow of mice which were recovering or had recovered from some form of depopulation. From the data obtained, the mean CFU-S/colony, M1, and the probability of self-renewal, p, of the CFU-S were calculated. These values are used to calculate the number of cell cycles undergone during development of the colony and, by making certain assumptions, the cell cycle time of the CFU-S. The plot of p against log M for the various samples measured should be linear if all CFU-S proliferate at the same rate in a growing colony. It is not linear, however, so that CFU-S obtained under different experimental conditions do not all undergo the same number of cycles. In general, treatments given to the mice result in a lowering of the capacity for self-renewal of their CFU-S and also to a shortening of their cell cycle time. Some of the possible implications of these findings are discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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