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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 137 (1988), S. 337-345 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Highly purified human erythroid colony-forming cells (ECFC), which consist predominately of colony-forming units-erythroid (CFU-F), were prepared from human blood and used to study the binding and processing of erythropoietin (Ep). When radioiodinated human recombinant Ep (125I-rEp) was incubated with these cells, binding was specific and saturable. Specific binding was directly proportional to cell concentration and did not occur with other human cells. Saturation of specific binding at 3°C occurred at 1 nM (3.9/U/ml), and Scatchard analysis revealed two classes of binding sites on the cell surface. Of a total of 1,050 binding sites per ECFC, one-fifth had a Kd of 0.10 nM, while the remainder had a Kd of 0.57 nM. Specific binding was twofold greater at 37°C than at 3°C, and removal of surface-bound Ep with acid indicated that 125I-rEp was internalized into the cells after incubation at 37°C. Further incubation at this temperature showed a decline of cellular radioactivity, with a release of small molecular weight degradation fragments into the medium. These studies demonstrate two classes of receptors for Ep on normal human ECFC. Internalization and degradation of EP occur, and the biologic effect of the hormone is produced by a small number of Ep molecules, as demonstrated in murine erythroid progenitor cells.
    Additional Material: 7 Ill.
    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 149 (1991), S. 1-8 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The course of the differentiation and proliferation of the human erythroid burst-forming units (BFU-E) to colony-forming units (CFU-E) was directly investigated using a combination of highly purified BFU-E, a liquid culture system, and the following clonal assay. Highly purified human blood BFU-E with a purity of 45-79% were cultured in liquid medium with recombinant human erythropoietin (rEP) and recombinant human interleukin-3 (rlL-3) to generate more differentiated erythroid progenitors. The cultured cells were collected daily for investigating the morphology, the increment in the number of cells and the clonality. Ninety percent of purified BFU-E required not only rEP but also rlL-3 for clonal development. By 7 days of liquid culture, the total cell number increased 237 ± 20-fold above the starting cells, while erythroid progenitors increased 156 ± 74-fold. As the incubation time in liquid culture increased, the cells continuously differentiated in morphology. Replating experiments with rTEP combined with or without rlL-3 showed the following: (1) The number of erythroblasts that were part of erythroid colonies decreased with accompanying erythroid progenitor differentiation and proliferation. (2) As the incubation time in liquid culture increased, erythroid progenitors had a graded loss of their dependency on rlL-3 and a complete loss of dependency was observed after 3 days of liquid culture. At that time 85% of the erythroid progenitors gave rise to colonies of more than 100 erythroblasts which were equivalent to mature BFU-E. These studies provide a quantitative assessment of the loss of lL-3 dependency by BFU-E and indicate that the size of the generated erythroid colonies and their lL-3 requirement correlate with the erythroid differentiated state.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: To facilitate the direct study of the molecular events that control the development of human burst-forming units-erythroid (BFU-E), we have developed a method to purify BFU-E from peripheral blood. Using density centrifugation, rosetting with a mixture of neuraminidase-treated and IgG-coated sheep erythrocytes, positive panning with anti-My10 monoclonal antibody, overnight adherence to plastic dishes, negative panning with monoclonal antibodies, and density centrifugation, human blood BFU-E were purified from 0.04% to 56.6%, a 1,400-fold purification with a 13% yield. More than 90% of purified BFU-E were recombinant interleukin-3 (rlL-3) dependent, which survived for 48 h with rlL-3 in the absence of recombinant erythropoietin (rEP), and 80% gave rise to erythroid bursts of more than 500 hemoglobinized cells. rEP dependency was not evident until after 72 h of incubation in vitro. The purified cells (day 1) were incubated with rlL-3 and rEP in liquid culture for 24 (day 2), 48 (day 3), and 72 (day 4) h and then were transferred into semisolid cultures and incubated until day 15. The size of the erythroid colonies observed in semisolid cultures decreased continuously in association with the incubation time of day 1 purified cells in liquid cultures. The first appearance of colony-forming units-erythoid (CFU-E) that gave rise to colonies of 8 to 49 cells was observed after 72 h of incubation of day 1 cells in the liquid culture. 125I-rEP was incubated for 5 h at 37°C with purified cells (day 1) or with the cells that had been incubated in liquid culture for an additional 24-72 h, and the presence of erythropoietin (EP) receptors was investigated using auto-radiography. Specific binding of 125I-rEP was detected in 19 ± 7% of the initial day 1 BFU-E. The percentage of 125I-rEP-binding to erythroid progenitor cells and the amount of binding continuously increased as day 1 BFU-E matured. 125I-rEP specific binding was observed with all of the erythroid progenitor cells that had been incubated in liquid culture for 72 h. These data demonstrate that primitive BFU-E have a much lower number of EP receptors than CFU-E and develop an increased concentration of EP receptors in association with their maturation and loss of proliferative capacity.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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