Frequency of T-Cell Progenitors in Nude Mice

The hypothesis that prothymocytes are distinct from and regulated independently of multilineage hemopoietic progenitors was tested by enumeration of these two cell populations in normal versus congenitally athymic (nude) mice. The absence of a thymus and of peripheral T cells in nude mice had no effect on the frequency of either multilineage progenitors (day 12 CFU-S) or prothymocytes (CFU-T), suggesting that there is no feedback regulation of CFU-T frequency. Thymus seeding from the bone marrow is therefore likely to be regulated by the availability of niches for prothymocyte maturation, rather than by feedback control of prothymocyte production.     

The influence of in vivo incubation of aged murine spleen colony-forming units on their proliferative capacity

Bone marrow cells from young and old mice (C3H/HeMs) were transplanted into irradiated syngeneic recipients. The growth rates of spleen colonies in both groups were compared by measuring the mean volume of colonies. Growth rates in spleen colonies derived from bone marrow cells of 462-day-old mice (Y-R) were higher than those from 917-day-old mice (O-R). Bone marrow cells from 62-day-old mice and those from 642-day-old mice were injected into 112-day-old irradiated (950 rad) recipients and after 400 days were killed. The bone marrow cells were assayed for spleen colony-forming units (CFU-S) and injected into irradiated secondary recipients, 50-55 days of age (Y-M-R and O-M-R). The cellular age at testing was 462 and 1042 days, respectively. The growth rates of colonies from young mice (Y-M-R) and from old ones (O-M-R) were similar in contrast to the first experiment in which the younger CFU-S produced more rapidly growing colonies. These studies clearly show that CFU-S from 462-day-old mice produce larger splenic colonies than CFU-S from 686- or 917-day-old mice. However, spleen colonies formed by CFU-S with cellular ages of 462 days (62 days + 400 days in vivo) and 1042 (642 days + 400 days in vivo) are not significantly different, suggesting that "in vivo incubation" has removed some of the proliferative defect of the 642-day-old CFU-S.     

生脉散对小鼠多能造血干细胞（CFU－S）影响的实验研究

生脉散系著名古方,广泛用于多种疾病所致“气阴两虚”证。采用符合该证的实验性骨髓抑制及贫血小鼠,以脾集落法等项技术观察生脉散对小鼠血发生的影响。将对照组与实验组进行比较,结果显示：生脉散可刺激多能造血干细胞增殖（Ｐ＜０．０５）,骨髓有核细胞增生（Ｐ＜０．０５）,白细胞增生（Ｐ＜０．０１）,对Ｈｂ及红细胞作用不明显（Ｐ＞０．０５）．结合其他学者的工作,推测生脉散的“益气养阴”作用与影响血发生功能有关。     

乌贼墨制品促进小鼠造血功能的实验研究

目的:观察乌贼墨制品对小鼠造血功能的影响。方法:用不同剂量的乌贼墨制品分别灌胃正常小鼠和环磷酰胺所致骨髓造血损伤模型小鼠,采用造血祖细胞体外培养方法和实验血液学技术,检测小鼠骨髓有核细胞数、骨髓造血干细胞数、粒单系祖细胞数和外周血WBC、RBC,PLT,Hb和网织红细胞。结果:乌贼墨制品能够显著提高正常小鼠骨髓有核细胞、造血干细胞、粒单系祖细胞和外周血WBC数量;对环磷酰胺所致骨髓造血损伤有显著的拮抗作用和促进其恢复;对正常小鼠和模型小鼠外周血RBC,PLT,Hb和网织红细胞均无显著性影响。结论:乌贼墨制品能够促进骨髓造血。其作用途径可能通过调节机体的免疫机能,诱导产生多种细胞因子,促进造血干细胞、粒单系祖细胞的增殖,并向粒系分化,促进小鼠的粒系造血。     

有机锗的抗放射作用

ICR小鼠受致死量射线照射以后,接受有机锗治疗14天.剂量为500mg/kg的小鼠30天活存率比对照组提高37.5％;当Ce—132剂量为500mg/kg和1000mg/kg时,其内源性脾结节的数量明显地高于对照组。实验结果表明,Ce—132具有一定的治疗急性骨髓型放射病的作用和刺激内源性造血干细胞的增殖与分化作用。     

A long lasting proliferative defect in the hematopoietic stem cell compartment following cytotoxic agents.

We have reported a significant proliferative defect caused by busulfan and L-phenylalanine mustard (L-PAM) while cyclophosphamide and 5-fluorouracil (5-FU) did not cause such a defect as measured by serial transplantation of bone marrow up to 110 weeks after drug administration. If the proliferative capacity of the initial colony-forming units (CFU-S) as expressed by the ratio (Rs) of the number of CFUs recovered (after 14 days) compared to the number seeding the hind limb prior to transplantation is determined, one finds that the R_S correlates with the defect in serial transplantation. Thus, damage to the proliferative capacity of the hematopoietic stem cell caused by chemotherapeutic agents can be expressed in terms of R_S, a measure of the self-renewal potential of the stem cell compartment.If R_S is assessed after a single drug injection, the pattern of the rise and decline of R_S with time following injection offers an efficient method of classifying drug injury to the CFU-S compartment. Busulfan was found to be the most damaging since it killed the most primitive stem cells preferentially. 5-FU was found to be the least damaging to the proliferative capacity of the stem cell compartment while BCNU and cyclophosphamide damaged it in an intermediate way. Therefore, busulfan would be expected to be most damaging to the normal hematopoietic tissue, followed by BCNU, cyclophosphamide and 5-FU in descending order of risk.     

Effects of thymocytes on marrow cells from normal and busulfan-treated mice

To study the effects of thymocytes on hemopoiesis, we 1) cocultured marrow cells with and without thymocytes in an erythroid burst (BFU-E) culture system, 2) injected marrow cells with and without thymocytes into supralethally irradiated mice to assay CFU-S, and 3) assessed the survival of supralethally irradiated mice transplanted with marrow cells with or without thymocytes. The marrow cells used were either from mice given six injections of busulfan and then permitted to rest for 2, 5, or 10 weeks or from mice treated similarly with the busulfan vehicle alone. Thymocytes did not alter spleen surface colony counts or survivorship in any of the test groups. Thymocytes did effect an increase in BFU-E cultured from marrow obtained from the vehicle-treated mice but not from marrow of busulfan-treated mice. Thus, in addition to decreasing the population of hemopoietic precursors in the marrow, busulfan alters the nature of the remaining early erythroid precursor cell population rendering it unresponsive to thymocytes in vitro.     

Evaluation of diethyldithiocarbamate as a radioprotector of bone marrow

The radioprotective action of DDC on normal hematopoietic tissue in mice was evaluated. An increase in CFU-S and CFU-GM in DDC treated unirradiated control mice was consistently observed. When post-irradiation survival of CFU-S and CFU-GM from DDC treated animals was normalized to account for this observed increase, protection factors ranging from 0.9 to 1.6 were observed. These protection factors are significantly lower than those reported by others. Maximum radioprotection was observed when irradiations were performed 15 to 30 min after DDC treatment; maximum increase in GFU-GM occurred within one to two hr following treatment. The increase in CFU-GM is analogous to that observed in animals treated with endotoxin, a non-thiol radioprotector. When C3H/HeJ mice, which are genetically incapable of responding to endotoxin, were challenged with DDC, an average CFU-GM increase of 1.7 times was observed, suggesting that the stimulatory effects of DDC were not due to endotoxin contamination. DDC was administered daily for three days before irradiation and little or no increase in CFU-GM and no radioprotection was observed, suggesting that the marrow can become refractory to DDC. When WR-2721 was tested in similar studies, a dose-modifying radioprotection was observed, with no significant non-specific stimulation of hematopoietic cells.     

Pluripoietin effects on CFU-S lineage determination: possible mechanisms

Regulation of pluripotent stem cell (CFU-S) proliferation kinetics by humoral factors is now well documented. However, the mechanism of choice of CFU-S differentiation pathways is still a controversial issue. We suggest that long-range humoral factors (pluripoietins) are capable of preferentially channelling CFU-S towards one of the cell lineages after various perturbations such as irradiation and drug treatment. The differentiation pathway depends on the treatment protocol. We present data concerning one of the protocols: injection of 20 mg of cytosine arabinoside (Ara-C). When conditioned medium from bone marrow of treated mice is incubated with normal marrow, CFU-S of the latter generate spleen colonies with an E/G ratio above normal values. Clonal analyses of spleen colonies demonstrate that they are generated by pluripotent stem cells. Therefore, any modification in the E/G ratio is due to modifications of CFU-S channelling and not to the variations of committed cells. It was of interest to determine the mechanism of pluripoietin activity. This was studied at three levels: membrane receptors, gene activation and protein synthesis. These studies suggest that CFU-S have receptors for pluripoietins which activate genes responsible for specific mRNA synthesis. De novo synthesis of proteins is a necessary prerequisite for pluripoietin activity to be expressed. Hypotheses for these mechanisms are presented.