Full-length but not truncated CD34 inhibits hematopoietic cell differentiation of M1 cells

CD34 is expressed on human and murine hematopoietic stem and progenitor cells and its clinical usefulness for isolation of stem/progenitor cells has been well established. Although expression of CD34 is regulated in a developmental stage-specific manner, the function of CD34 is not known. Recently we have shown that both a full-length and truncated form of CD34 protein is expressed by hematopoietic cells (Blood 84:691, 1994). To test whether failure to suppress either form of CD34 could affect terminal myeloid differentiation, we constitutively expressed these CD34 proteins in murine M1 myeloid leukemia cells, which can be terminally differentiated to macrophages by treatment with interleukin-6 of leukemia inhibitory factor. Surprisingly our results show that forced expression of the full-length but not the truncated form of CD34 impedes terminal differentiation by these agents. Because the difference between the two forms of CD34 protein resides in the length of their respective cytoplasmic tail domains, our findings strongly suggest that the cytoplasmic domain region of full-length CD34 is responsible for the observed maturation arrest phenotype. These findings suggest a potential negative regulatory role for full-length CD34 in hematopoietic cell differentiation and may explain, at least in part, the block in maturation observed in CD34+ acute myeloid leukemia.     

Deleterious effect of brachtherary on vasomotor response to exercise

Background In-stent restenosis(ISR) is one of the major drawbacks of coronary stenting. Intraeoronary radiation therapy (RT)is effective in reducing excessive neointimal proliferation but long term results with regard to vascular integrity and vasomotor responsiveness are largely tmknown. Thus, the present study was to determine the exercise-induced vasomotor response of inadiated coronary arteries.     

Prevalence of hypochromia (without microcytosis) vs microcytosis (without hypochromia) in iron deficiency

The usefulness of hypochromia (MCH or = 80 (fl) vs. counterparts with MCV < 80 fl (in the presence of MCH > or = 26 pg). Fifteen per cent of the 201 iron deficient subjects were also shown to have coexisting vitamin B12 deficiency. There was a comparable (16%) prevalence of this haematinic deficiency in the subgroup of 31 iron deficient patients with MCH < 26 pg in the presence of MCH > or = 80 fl.