Different marrow cell number requirements for the haemopoietic colony formation and the cure of the W/Wv anemia

Summary The lowest cell number in the normal marrow transplant, which allows the cure of W/W^v anemia was found to be between 10⁴ and 10⁵. This exceeds by several times the lowest cell number necessary for the haemopoietic colony formation. Therefore, either the colony forming cell is not the haemopoietic stem cell but rather its progeny, or this cell requires an aid from some other cells to exert its activity.Acknowledgments. We are indebted to Doc. Dr Maksymilian Siekierzynski for his help and advice and to Miss Elzbieta Szewczyk for expert technical assistance.     

Separation of pluripotent haematopoietic stem cells from spleen colony-forming cells

Long-term reconstitution of the lymphohaematopoietic cells of a mouse after lethal irradiation requires the transplantation of at least (5-10) x 10(3) bone marrow cells. Several cell-separation techniques based on cell-surface characteristics have been used in attempts to identify the pluripotent haematopoietic stem cells (PHSC), and have allowed the long-term engraftment of lethally irradiated mice with an enriched fraction of fewer than 200 marrow cells. But these techniques enrich not only for PHSC but also for haematopoietic progenitors, especially day-12 spleen colony-forming units (CFU-S). Although day-12 CFU-S have been postulated to be primitive multipotential haematopoietic progenitors, with day-8 CFU-S representing later, more committed progenitors, recent evidence suggests that neither of these CFU-S represents mouse PHSC. Here we report that counterflow centrifugal elutriation, which sorts cells on the basis of size and density, can separate PHSC from these less primitive progenitors. The fraction containing the largest cells was enriched for the granulocyte-macrophage colony-forming units (CFU-GM), but gave only transient, early engraftment and was therefore depleted of PHSC. The intermediate fraction was enriched for CFU-S, but depleted of CFU-GM. Despite being devoid of CFU-GM and CFU-S, the fraction consisting of only morphological lymphocytes gave sustained, albeit delayed, reconstitution of all lymphohaematopoietic cells, and was therefore enriched for PHSC. We conclude that there are two vital classes of engrafting cells: committed progenitors, which provide initial, unsustained engraftment, and PHSC, which produce delayed, but durable, engraftment. Therefore for late haematological reconstitution, PHSC must be transplanted with a distinguishable source of early engrafting cells, thereby allowing the lethally irradiated host to survive initial aplasia.     

Different marrow cell number requirements for the haemopoietic colony formation and the curve of the W/Wv anemia.

The lowest cell number in the normal marrow transplant, which allows the cure of W/Wv anemia was found to be between 10(4) and 10(5). This exceeds by several times the lowest cell number necessary for the haemopoietic colony formation. Therefore, either the colony forming cell is not the haemopoietic stem cell but rather its progeny, or this cell requires an aid from some other cells to exert is activity.     

Pixel switching of epitaxial Pd/YHx/CaF2 switchable mirrors

Exposure of rare-earth films to hydrogen can induce a metal-insulator transition, accompanied by pronounced optical changes. This 'switchable mirror' effect has received considerable attention from theoretical, experimental and technological points of view. Most systems use polycrystalline films, but the synthesis of yttrium-based epitaxial switchable mirrors has also been reported. The latter form an extended self-organized ridge network during initial hydrogen loading, which results in the creation of micrometre-sized triangular domains. Here we observe homogeneous and essentially independent optical switching of individual domains in epitaxial switchable mirrors during hydrogen absorption. The optical switching is accompanied by topographical changes as the domains sequentially expand and contract; the ridges block lateral hydrogen diffusion and serve as a microscopic lubricant for the domain oscillations. We observe the correlated changes in topology and optical properties using in situ atomic force and optical microscopy. Single-domain phase switching is not observed in polycrystalline films, which are optically homogeneous. The ability to generate a tunable, dense pattern of switchable pixels is of technological relevance for solid-state displays based on switchable mirrors.     

大叶白麻叶化学成分的研究

从大叶白麻[poacynumhendersonii(Hookf)woodson]叶中分得2个木脂素类化舍物,经理化常数测定和光谱分析,分别鉴定为(-)-丁香脂素[(-)-Syringaresino1]和( )-松脂素-4-O-β-D-葡萄糖甙[( )-Pinoresionol-4-0-β-D-glucopyranoside].