Study on a fraction with relative radioresistency from murine pluripotent hemopoietic stem cells.

根据我们对胸腺嘧啶细胞杀虫剂的研究，脾脏菌落形成单位（CFLJ-S）可以。被分成两个主要部分；即分化多能性较差的干细胞，主要处于S期（祖细胞产生早出现的集落），而其他具有静止性质的干细胞没有细胞周期（祖细胞产生晚出现的集落）。前者对各种造血刺激的反应程度较大，后者对各种造血刺激的反应程度相对较小。如上所述，CFU-S的异质性表明，在每个子部分中都存在异质性的辐射敏感性，然而，没有一个实际证明与这种异质性辐射敏感性有关。用400 ~ 600 eGy辐照骨髓细胞，体外注射致死性辐照小鼠，形成脾脏菌落。在这些相对较大剂量的辐射后，发现了一个分数，其程度比单指数模型的生存曲线拟合估计的数字更大；即，陡峭的规则生存曲线（D_0=90 cGy）在300至400 cGy后变为平坦的生存曲线（D_0=270 cGy），可能是由于一个小的辐射敏感亚分数（约3-5%）混合。使用常规的CFLJ-S。在我们的研究项目中，各种不同的小鼠标本证实了这一点。虽然辐照是在体外进行的，但氧效应必须是最小的或没有，实际上，在生存曲线的这些平坦部分的机制中可能没有影响，因为每个部分的总辐射时间约为4分14秒或更少。在这些研究中，我们偶然在Scid小鼠中发现了与CFLJ-S的辐射抗性部分有关的另一个重要发现。最初，由于双链断裂修复的功能缺陷，已经发现Scid突变中的体细胞具有非常低的抗性。我们发现，在D_0的监测下，Scid小鼠再次出现了与常规CFU-S明显不同的相对耐辐射部分。这一现象将与本研究计划的进一步研究有关。少

According to our suty on tridated thymidine cytocide, a colony forming unit in spleen (CFLJ-S) can. be divided into two major fractions ; i. e. stem cells possessing less pluripotency in differentiation with a Idnetics largely in S phase (the progenitor cells producing early appearing colonies), and the other ones possessing quiescent nature without cell cycle (the progenitor cells producing late appearing colonies). While former fraction reacts at larger extent to a variety of hemopoietic stimuli, latter does but relatively at a smaller extent. The heterogeneity of the CFU-S, as seen above, suggestes a heterogeneous radiation sensifivity in 6ach sub-fraction, however, none has been actually demonstrated pertaining to this heterogeneous radiation sensitivity. Bone marrow cells were irradiated with 400 cOy through 600 eGy, in vitro, and then been injected with lethally irradiated mice to form spleen colonies. There was a fraction found after these relatively larger dose of radiation at … More larger extent than numbers estimated by a survival curve fitting to a single-exponential model ; namely, the steep regular survival curve (D_0=90 cGy) changed into a flatter bne (D_0=270 cGy) after 300 through 400 cGy, probably because of a small radiosensitive subfraction, ca. 3-5%, mixed. with the regular CFLJ-S. This was confirmed by a variety of different murine stanns in our research project. Although irradiation was given at in vitro, oxygen effects must be minimum or none, and actually, no effects might have been involved in a mechanism of these flatter part of the survival curve, since total radiation time took for each fraction was ca. 4 min. and 14 sec. and or less. During these studies, we incidentally found another important finding in the Scid mice pertaining to the radioresistant fraction of the CFLJ-S. Originally, somatic cells in Scid mutaidon have been found to be very mioresistant because of a functional defect of repair for double strand breaks. We found, under the surveillance of D_0 in the Scid mice, again, a relatively radioresistant fraction sharply defined from the regular CFU-S. This phenomenon would deal with further study of this research program. Less