人胚胎干细胞分化为神经干细胞诱导方法的对比研究

目的探讨人胚胎干细胞分化为神经干细胞过程中,经拟胚体（embryonic body,EB）法和直接分化法的不同效率。方法人胚胎干细胞常规培养消化后,分为两组：A组,经EB法分化;B组,添加noggin和ITSFn直接分化法。倒置相差显微镜观察细胞形态变化,RT-PCR检测细胞各阶段标志物,免疫荧光及流式细胞仪观察两组细胞Nestin阳性细胞率。神经干细胞继续分化,免疫荧光、RT-PCR法检测MAP2、GFAP表达。结果RT-PCR检测到OCT4、nestin表达。B组nestin阳性细胞率明显高于A组,差异有统计学意义（P〈0.01）,且诱导周期短于A组。神经干细胞继续分化,得到不同数量的神经元和胶质细胞,MAP2、GFAP分别阳性。结论在体外采用定向分化诱导,人胚胎干细胞不经EB,可直接定向分化为神经干细胞,且诱导效率比EB法高。因此直接分化法是一种经济实用的诱导方法。     

BASAL STEM ANATOMY OF PSARONIUS

The basal stem anatomy of three young sporophytes of Psaronius from the Middle Pennsylvanian of Kansas and Illinois is described. The origin of the second stelar cycle is demonstrated in the transition from a simple, amphiphloic siphonostele to a dicyclic dictyostele. Petioles with C-shaped vascular strands are attached to the stem in a one-third phyllotaxy. A root mantle is lacking. Basal stem anatomy of Psaronius is compared with that of living genera of the Marattiaceae.     

STEM tomography in cell biology

Transmission electron tomography has been used in biological sciences for quite some time and proven to be a valuable tool. However, to date, the different Scanning Transmission modes are almost not used for electron tomography on resin-embedded biological material. We explored different STEM modes on epon-embedded, osmium-uranyl-lead-stained biological material. Bright Field-TEM and High Angle Annular Dark Field-STEM tomograms from the same areas were recorded and compared. Contrast and signal-to-noise ratios were calculated. Template matching was used to validate results obtained in Bright Field-TEM and High Angle Annular Dark Field-STEM tomograms. It is concluded that High Angle Annular Dark Field-STEM gives a five times better contrast and signal-to-noise ratio than Bright Field-TEM. Template matching showed that 1.3 times more information could be extracted from High Angle Annular Dark Field-STEM tomograms than from Bright Field-TEM tomograms.     

小鼠胚胎干细胞定向分化为神经干细胞过程中microRNA的变化

目的用生物芯片技术分析胚胎干细胞定向分化为神经干细胞过程中microRNA(miRNA)的表达变化,筛选调控的分化的miRNA,研究分化调控机制。方法胚胎干细胞在含LIF培养基中培养3d后,采用经典5步培养方法定向诱导向神经干细胞分化,采用nestin作为神经干细胞标记进行鉴定,送检胚胎干细胞及神经干细胞,提取总RNA以及小分子RNA,经荧光标记后与miRNA基因芯片杂交,获得胚胎干细胞诱导前后miRNA表达谱。结果1)胚胎干细胞在含LIF培养过程中保持未分化状态,Oct-4、碱性磷酸酶表达阳性;2)经典五步法诱导胚胎干细胞定向分化为神经干细胞,nestin阳性细胞为85%;3)通过基因微阵列分析,有90个miRNA的改变显著,其中68个表达上调,22个表达下调。结论miRNA可能对胚胎干细胞定向分化为神经干细胞过程起到关键作用。     

KINETIC PROPERTIES OF HAEMOPOIETIC STEM CELLS

A comparison of the exocolonizing and autorepopulating tests for haemopoietic stem-cell assay indicate that the ‘overshoot’in splenic colony formation, observed 12–14 days after 150 rad total-body radiation (TBR), only occurs with the auto-repopulation assay. The explanation is that the priming dose of 150 rad increases the absolute seeding rate of stem cells from the marrow. A seeding rate significantly greater than normal can ‘take’only if the spleen is available—it can expand and accommodate stem cells while the bone marrow cannot. If, however, the absolute number of colony-forming cells are decreased in the femur, a relative increase in seeding rate can take place even in the splenectomized animal. Evidence is presented concerning the different turnover states of exo- and autorepopulating stem cells (CFU) and those responsible for erythropoietic response (ERC), and the precursors of agar colony-formers.     

PATTERNS OF STEM VASCULATURE IN PHILODENDRON

A survey of 480 collections of stem material of Philodendron has established five patterns of vascular organization. Species representing each of these patterns were analyzed by cinematographic methods to allow a three-dimensional interpretation of the course of vascular bundles over extended distances. Pattern 1 has mainly collateral organization, but with some bipolar bundles. Pattern 2 has a majority of central bundles aggregated into compound (multipolar) bundles; Pattern 3 differs in that almost all bundles of the central cylinder are multipolar. Patterns 4 and 5 include compound vascular bundles in which the individual strands are not very discrete so that in Pattern 5, which is the most common in the genus, the bundles might be described as amphivasal. In Section Pteromischum, which has monopodial construction, the majority of species exhibit Pattern 2 which is exclusive to this group. Other correlations with subgeneric groupings are emphasized.     

STEM ABSCISSION IN THE TUMBLEWEED,PSORALEA

Abscission was studied in Psoralea argophylla Pursh, a prairie tumbleweed. This process is responsible for the detachment of the stem from its perennial base. In a single plant abscission may proceed through one or more intercalary meristems located at or near ground level. During senescence a separation layer differentiates within each of these meristems. Chemical changes occur within the compound middle lamellae which result in the conversion of insoluble pectic compounds into soluble forms. Cell separation takes place only after removal of the pectic compounds, meristematic activity, and attenuation of cell walls. Unlike reports of other angiosperms the protective layer is not formed adjacent to the separation layer, but forms some distance underground at the stem-root junction.     

小钩叶藤茎解剖特性的变异

试验材料为一株２６０节、长约４２ｍ的小钩叶藤（ＰｌｅｃｔｏｃｏｍｉａｍｉｃｒｏｓｔａｃｈｙｓＢｕｒｒｅｔ）．分析了藤茎下列特性的轴向变异：表皮细胞的垂周长度和外壁厚度、皮层宽度、维管束的密度和纤维鞘／维管组织比值、后生木质部导管分子的长度和宽度、纤维长度,以及节间的长度和直径。节间长度、导管分子长度及纤维长度的轴向变异一致．这三项特性反映茎的生长活力．     

HAEMOPOIETIC STEM CELLS IN EXPERIMENTAL HAEMOLYTIC ANAEMIA

Phenylhydrazine treatment produced an expansion of spleen CFU (10 x N) and an even greater expansion of spleen ACFU (40 x N). Blood CFU and ACFU levels also increased. While marrow CFU did not change marrow ACFU showed a pronounced drop. The ratio of ACFU/CFU varied between tissues, it was highest in marrow and lowest in peripheral blood. The changes in CFU, ACFU and blood granulocytes are discussed in relation to the radioprotective action of phenylhydrazine pretreatment of mice.