Shekhter-Levin S, Amato D, Karrass L, Axelrad A A
Exp Hematol. 1985 Dec;13(11):1138-42.
Normal human blood BFU-E are believed to be in a quiescent state with respect to DNA synthesis, since few or none of these progenitors can be killed by cycle-active agents. Using Percoll discontinuous density gradient centrifugation of normal human blood mononuclear cells, we have separated two subpopulations of BFU-E with different proportions in DNA synthesis. Mononuclear cells were obtained with Ficoll-Isopaque from 24 samples of normal blood. BFU-E were assayed with the methylcellulose technique, and their proliferative state was studied with the hydroxyurea (HU) suicide method. The results obtained with a five-step gradient of density range 1.060-1.068 g/ml showed that the vast majority of BFU-E were distributed approximately equally between pooled fractions with rho = 1.060 + 1.062 g/ml and those with rho = 1.064 + 1.066 g/ml. Among nonseparated cells or cells in the fraction of rho = 1.060 + 1.062 g/ml, we failed to detect a significant proportion of DNA-synthesizing BFU-E in the great majority of samples. In contrast, in the pooled fractions with rho = 1.064 + 1.066 g/ml, 14 of 24 samples showed significant kill, and among these 14, a highly significant proportion of BFU-E were killed by HU (39.3% +/- 3.4%). Therefore, the separation of mononuclear cells on the basis of their different buoyant densities revealed the presence of DNA-synthesizing BFU-E in normal human blood. Either DNA-synthesizing BFU-E have a higher buoyant density than non-DNA-synthesizing BFU-E, or else cells of lower buoyant density normally inhibit DNA synthesis in BFU-E.
正常人体血液中的爆式红系集落形成单位（BFU-E）被认为在DNA合成方面处于静止状态，因为这些祖细胞中很少或没有能被周期活性药物杀死的。通过对正常人血液单核细胞进行Percoll不连续密度梯度离心，我们分离出了两个在DNA合成比例上不同的BFU-E亚群。用Ficoll-Isopaque从24份正常血液样本中获取单核细胞。用甲基纤维素技术检测BFU-E，并通过羟基脲（HU）自杀法研究其增殖状态。在密度范围为1.060 - 1.068 g/ml的五步梯度实验中得到的结果表明，绝大多数BFU-E大致均匀地分布在ρ = 1.060 + 1.062 g/ml的合并组分与ρ = 1.064 + 1.066 g/ml的合并组分之间。在未分离的细胞或ρ = 1.060 + 1.062 g/ml组分中的细胞中，我们在绝大多数样本中未能检测到显著比例的正在进行DNA合成的BFU-E。相比之下，在ρ = 1.064 + 1.066 g/ml的合并组分中，24个样本中有14个显示出显著杀伤，在这14个样本中，有很高比例的BFU-E被HU杀死（39.3% ± 3.4%）。因此，根据单核细胞不同的浮力密度进行分离揭示了正常人血液中存在正在进行DNA合成的BFU-E。要么正在进行DNA合成的BFU-E比不进行DNA合成的BFU-E具有更高的浮力密度，要么浮力密度较低的细胞通常会抑制BFU-E中的DNA合成。
