CFU-E cells

Babies, especially babies born prematurely, often exhibit anaemia, which is characterized by a steadily decreasing serum haemoglobin level during the first 8 weeks of life. While multiple factors contribute to development of anaemia of prematurity, a lower than normal serum EPO level is a characteristic trait. In vitro studies indicate that BFU-E and CFU-E cells from such babies are responsive to EPO, and several pilot clinical trials have been initiated. Administration of 300-600 lU EPO/kg/week generally was found to enhance erythropoiesis and reduced the number of transfusions required by up to 30%. 

Through in vitro culture systems, one BFTJ-E can proliferate into several hundred progeny. These cells are followed in differentiation hy the CFU-E cell, and subsequently hy the nucleated normoblast and the immediate RBC precursor, the circulating anuclear reticulocyte as outhned in Fig. 98-3. The remaining RNA is typically lost from the RBC within 2 days of its appearance in the peripheral blood thus the mature cell does not synthesize new proteins such as enzymes. ... 

Erythropoiesis is a process that starts with a pluripotent stem cell in the bone marrow that eventually differentiates into an erythroid colony-forming unit (CFU-E)4 (Fig. 63-1). The development of these cells depends on stimulation from the appropriate growth factors, primarily erythropoietin. Other cytokines involved include granulocyte-monocyte colony-stimulating factor (GM-CSF) and interleukin 3 (IL-3). Eventually, the CFU-Es differentiate into reticulocytes and cross from the bone marrow into the peripheral blood. Finally, these reticulocytes mature into erythrocytes after 1 to 2 days in the bloodstream. Throughout this process, the cells gradually accumulate more hemoglobin and lose their nuclei.4... 

The effects of Li+ upon hematopoiesis have been proposed to be due to two different systems modification of the activity of the membrane Na+/K+-ATPase, and the inhibition of adenylate cyclase. Monovalent cation flux, in particular Na+ transport, is known to influence the differentiation and proliferation of hematopoietic stem cells. For instance, ouabain, an effective inhibitor of the membrane Na+/K+-ATPase, blocks the proliferation of lymphocytes and has been shown to attenuate the Li+-induced proliferation of granulocyte precursors [208]. Conversely, Li+ can reverse the actions of amphotericin and monensin, which mediate Na+ transport and which inhibit CFU-GM, CFU-E, and CFU-MK colony formation in the absence of Li+ [209]. Therefore, the influence of Li+ upon normal physiological cation transport—for example, its influence upon Na+/K+-ATPase activity—may be partly responsible for the observed interference in hematopoiesis. 

The last potential mechanism to be discussed in this chapter is drug-induced altered receptor expression. Hematopoiesis is a very intricate process that is regulated by cytokines and cell-cell interactions. Interruption with any of these processes can result in hematotoxicity. For example, zidovudine (AZT) decreases Epo [27], GM-CSFaand to lesser extent IL-3 receptor expression [7]. Decrease in the expression of the above receptors seems to lead to anemia and neutropenia, by decreasing the number of CFU-E and CFU-GM, respectively. 

Some perturbation of the reticulocyte numbers was observed, but values at days 3 and 5 did not differ from controls. Absolute numbers of lymphocytes and neutrophils did not differ from controls (no data shown). A slight anemia was observed at 4 and 8 weeks of treatment with 300 and 900 ppm benzene. Results showed minor changes in the stem and progenitor cells. CFU-E depression after 4 days of exposure was significant. There was a dose-dependent depression of colony forming cell numbers present at 4 and 8 weeks of exposure with a maximal effect at the level of CFU-E. Decreased CFU-E and BFU-E were observed in a companion study in which hybrid mice were exposed to 300 or 900 ppm benzene for the same period of time (Plappert et al. 1994b). 

Alterations in hematopoiesis have also been observed in the fetuses and offspring of pregnant mice exposed to benzene (Keller and Snyder 1986). Administration of 20 ppm benzene to pregnant Swiss Webster mice for 6 hours per day on Gd 6-15 caused reductions in the levels of the CFU-E of the fetuses, whereas 5 and 10 ppm benzene caused enhancement of these colony-forming cells. In 2-day-old neonates, CFU-E numbers in the 5 ppm group returned to control values, but the 10 ppm neonates showed a bimodal response by litter. Granulocytic colony-forming cells were enhanced in neonates exposed in utero to 20 ppm benzene. Some of the mice exposed to 10 ppm prenatally were re-exposed to 10 ppm as... 

Gailicchio, V. S Casale, G. R, and Watts, T, (1987b). Inhibition of human bone marrow-derived stem cell colony formation (CFU-E, BFU-E, and CFU-GM) following in vitro exposure to organophosphaies. FLxp. Hematol. 15, 1099-1102. 

E.coli recA y.luxCDABE strain were grown for 16-18 hours at 37°C in LB-broth in the presence of 20 pg/ ml of ampicillin. Immediately before the experiment the culture was diluted 1 20 by fresh culture medium and incubated until early log-phase. The grown biomass was mixed with AR solutions in final concentrations of ICfs, ICH n ICfs M, with used for their dilution with distilled water (control) and incubated for 60 minutes. The luminescence intensity of UV-irradiated E.coli recA lux and intact specimens were registered by plate bioluminometer LM OIT (Immimotech, Czech Rep.) in a real time. The number of viable cells was determined from the colony-forming units (CFU) on a surface of a LB-agar after the subsequent incubation within 24 hours at 37 °C. A quantitative estimation of an induction of the SOS-system calculated on formula... 

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