Control of the reversibility of cellular quiescence by the transcriptional repressor HES1

The mechanisms by which quiescent cells, including adult stem cells, preserve their ability to resume proliferation after weeks or even years of cell cycle arrest are not known. We report that reversibility is not a passive property of nondividing cells, because enforced cell cycle arrest for a period as brief as 4 days initiates spontaneous, premature, and irreversible senescence. Increased expression of the gene encoding the basic helix-loop-helix protein HES1 was required for quiescence to be reversible, because HES1 prevented both premature senescence and inappropriate differentiation in quiescent fibroblasts. In some human tumors, the HES1 pathway was activated, which allowed these cells to evade differentiation and irreversible cell cycle arrest. We conclude that HES1 safeguards against irreversible cell cycle exit both during normal cellular quiescence and pathologically in the setting of tumorigenesis.     

生长素和细胞分裂素在马铃薯愈伤组织分化中的作用

以晋薯7号马铃薯茎尖、茎段、叶圆片为外植体,通过愈伤组织的诱导和根、不定芽的分化,研究生长素和细胞分裂素不同配比在马铃薯愈伤组织分化中的作用。试验结果表明:6-BA 1.5 mg/L+NAA 1.0mg/L+3%蔗糖+0.6%琼脂有利于茎段愈伤组织的生长,MS+6-BA 2.0 mg/L+ZT 2.0 mg/L+NAA 0.5mg/L+GA35.0 mg/L+3%蔗糖+0.6%琼脂有利于茎尖不定芽的分化,MS+6-BA 1.5 mg/L+NAA 0.5mg/L+GA35.0 mg/L+3%蔗糖+0.6%琼脂对叶片根的分化效果较好。     

阻断大鼠骨髓间充质干细胞向脂肪细胞分化与肿瘤发生相关性研究

【目的】分析骨髓间充质干细胞在体外定向分化为脂肪细胞的适宜诱导条件.阻断正常干细胞的分化过程,探讨肿瘤发生机理.【方法】利用贴壁培养法获得大鼠骨髓间充质干细胞(bone marrow mesenchymal stem cells,BMSCs),通过地塞米松、胰岛素和吲哚美辛联合诱导大鼠BMSCs,使其分化为脂肪细胞.在细胞分化过程中利用3-甲基胆蒽(3-MC)阻断大鼠BMSCs的分化过程.【结果】大鼠BMSCs分化试验显示:诱导30d后经油红O染色,细胞内可见脂肪细胞特有的红色脂滴沉淀,并且随着诱导时间的延长,油红O阳性细胞比例增加,脂滴增大,表明大鼠BMSCs已成功分化为脂肪细胞.大鼠BMSCs分化阻断试验显示:诱导30d后经油红O染色细胞内红色脂滴沉淀明显下降,表明阻断后的细胞具有脂肪细胞的特性,但分化不完全;形态学鉴定表现出:细胞接触抑制消失,细胞核异常,微核畸变率高,核型异常,表明阻断后的干细胞发生恶性转变.【结论】通过地塞米松、胰岛素和吲哚美辛的联合作用,诱导BMSCs成功向脂肪细胞分化.在BMSCs向脂肪细胞分化的过程中加入阻断剂3-MC,阻断其分化过程,表明干细胞分化过程受到阻断,细胞停止在分化的中间阶段,有转化成肿瘤细胞的趋势.     

胡杨横走侧根及不定芽发生的形态解剖学研究

利用常规石蜡切片法对胡杨根蘖繁殖特性进行形态解剖学研究。结果表明：胡杨横走侧根的初生木质部为三原型或四原型,周皮中栓内层较发达,由6～8层薄壁细胞组成。横走侧根横切面上次生维管组织中次生韧皮部的比例远小于次生木质部;早期形成的次生木质部以细胞壁尚未木质化的木纤维细胞数量居多为特征;维管射线很发达。胡杨的根蘖繁殖源于横走...     

几种生长调节物质及有机附加物对菠萝愈伤组织分化影响的细胞学研究

用菠萝6－74冠芽诱导愈伤组织，在愈伤组织分化过程中进行细胞学研究，观察到菠萝伤组织中薄壁细胞随机分化形成胚性细胞，胚性细胞分裂形成两种分生组织即生细胞团和分生组织结节，它们可以进一步形成器官原基，分化为芽、根、苄氨基嘌呤（BA）对务组织芽的分化起决定性作用，它刺激分生细胞团产生单向极性生长形成芽原基。萘乙酸（NAA）则对根的分化起决定作用，玉米素（ZT）在有BA和NAA的存在下加速了细胞型分裂和分生组织向芽原基的分化，水解乳蛋白（LH）促进芽的分化，但却抑制维管组织结节向根的转化；。酵母提取液（YE）则对两种分生组织的进一步分化都有抑制作用。     

Direct control of germline stem cell division and cyst growth by neural insulin in Drosophila

Stem cells reside in specialized niches that provide signals required for their maintenance and division. Tissue-extrinsic signals can also modify stem cell activity, although this is poorly understood. Here, we report that neural-derived Drosophila insulin-like peptides (DILPs) directly regulate germline stem cell division rate, demonstrating that signals mediating the ovarian response to nutritional input can modify stem cell activity in a niche-independent manner. We also reveal a crucial direct role of DILPs in controlling germline cyst growth and vitellogenesis.     

Generalized potential of adult neural stem cells

The differentiation potential of stem cells in tissues of the adult has been thought to be limited to cell lineages present in the organ from which they were derived, but there is evidence that some stem cells may have a broader differentiation repertoire. We show here that neural stem cells from the adult mouse brain can contribute to the formation of chimeric chick and mouse embryos and give rise to cells of all germ layers. This demonstrates that an adult neural stem cell has a very broad developmental capacity and may potentially be used to generate a variety of cell types for transplantation in different diseases.     

植物干细胞研究进展

该研究从植物干细胞的概念、茎端分生组织与根端分生组织特征及其各自调控的分子基础等方面综述了当前植物干细胞研究的新进展,同时,阐述了植物干细胞发生与分化受到内源性信号和外源性信号的共同调节,分析了内源基因以及外源调控分子的相互作用,并对植物干细胞的研究进行了展望。     

Interconversion between intestinal stem cell populations in distinct niches

Intestinal epithelial stem cell identity and location have been the subject of substantial research. Cells in the +4 niche are slow-cycling and label-retaining, whereas a different stem cell niche located at the crypt base is occupied by crypt base columnar (CBC) cells. CBCs are distinct from +4 cells, and the relationship between them is unknown, though both give rise to all intestinal epithelial lineages. We demonstrate that Hopx, an atypical homeobox protein, is a specific marker of +4 cells. Hopx-expressing cells give rise to CBCs and all mature intestinal epithelial lineages. Conversely, CBCs can give rise to +4 Hopx-positive cells. These findings demonstrate a bidirectional lineage relationship between active and quiescent stem cells in their niches.     

Embryonic stem cells. Stem cell programs

The availability of human embryonic stem cell lines provides an important tool for scientists to explore the fundamental mechanisms that regulate differentiation into specific cell types. When more is known about the mechanisms that govern these processes, human embryonic stem cells may be clinically useful in generating cell types that have been damaged or depleted by a variety of human diseases. The NIH is actively pursuing a variety of initiatives to promote this developing research field, while continuing and expanding its long-standing investment in adult stem cells and research.     

精原干细胞的体外增殖与分化

最近,由于干细胞研究普遍取得的令人鼓舞的进展以及干细胞分离、培养、移植等新技术方法的出现和发展,出生后雄性个体的生殖系干细胞———精原干细胞(spermatogonialstemcell,SSC)已成为一个愈加引人瞩目的课题。SSC位于睾丸曲细精管基膜上,既具有自增殖(self-renewal)潜能和定向分化潜能,又是自然状态下出生后个体内在整个生命期间能够进行自增殖并能将基因传递至子代的惟一成体干细胞。了解干细胞增殖与分化的调节机制,获得足够数量的种子细胞一直是所有干细胞研究共同面临的迫切问题之一。近年来,借助于SSCs移植技术这一功能性检测方法,国内外学者就SSCs体外培养的条件进行了深入探讨,取得了可喜进展。结合自己的前期工作,参考相关最新进展,就影响哺乳类SSCs体外存活、增殖、分化的因素及未来需要解决的问题进行了评述。     

杏果实发育的形态解剖学研究

对杏果实发育过程进行了较系统的形态组织结构解剖学研究。结果表明 ,杏子房内有两个横生胚珠。果皮由外果皮、中果皮和内果皮构成。外果皮是一种复合结构 ,由表皮毛、表皮细胞和气孔器组成 ,中果皮主要是由薄壁细胞和分布其中的维管束组成 ,内果皮细胞经过分裂、分化形成 3种不同形态的细胞区域 ,最内部区域为垂直伸长的石细胞 ,中间区域为弦向伸长的石细胞 ,最外区域为等径的石细胞 ,其木质化顺序由外向内。合子细胞分裂经过球形胚和子叶形胚时期 ;胚芽的分化早于胚根     

缺磷胁迫对长豇豆幼苗乙烯产生量的影响

【目的】探讨乙烯在长豇豆幼苗耐缺磷胁迫中的作用。【方法】选用3个耐缺磷程度不同的长豇豆品种芦花白（耐缺磷）、香港青（中间类型）、二芦白（不耐缺磷），采用水培方式，设置供磷（＋P）和缺磷（－P）2个处理，研究其幼苗各部分在缺磷胁迫下乙烯产生量的变化。【结果】缺磷胁迫下长豇豆幼苗根系乙烯产生量升高，升幅芦花白>香港青>二芦白；老茎叶乙烯产生量升高，升幅二芦白>香港青>芦花白；最嫩完全展开叶乙烯产生量也升高，其中升幅芦花白>二芦白>香港青；嫩茎叶乙烯产生量有变化，但幅度较小。【结论】缺磷胁迫下长豇豆幼苗根系和老茎叶乙烯产生量升高可能导致植物根系和茎形态结构的变化，增强植物获取磷的能力和根系清除活性氧的能力，增强了植株对水分和养分的吸收运输能力，从而增强适应缺磷胁迫的能力。     

精原干细胞的体外增殖与分化

最近，由于干细胞研究普遍取得的令人鼓舞的进展以及干细胞分离、培养、移植等新技术方法的出现和发展，出生后雄性个体的生殖系干细胞——精原干细胞(spermatogonial stem cell, SSC)已成为一个愈加引人瞩目的课题。SSC位于睾丸曲细精管基膜上，既具有自增殖(self-renewal)潜能和定向分化潜能，又是自然状态下出生后个体内在整个生命期间能够进行自增殖并能将基因传递至子代的惟一成体干细胞。了解干细胞增殖与分化的调节机制，获得足够数量的种子细胞一直是所有干细胞研究共同面临的迫切问题之一。近年来，借助于SSCs移植技术这一功能性检测方法，国内外学者就SSCs体外培养的条件进行了深入探讨，取得了可喜进展。结合自己的前期工作，参考相关最新进展，就影响哺乳类SSCs体外存活、增殖、分化的因素及未来需要解决的问题进行了评述。     

Stem cell self-renewal controlled by chromatin remodeling factors

The self-renewing ability of a stem cell is controlled by its specialized micro-environment or niche, whereas epigenetic regulation of gene expression by chromatin remodeling factors underlies cell fate determination. Here we report that the adenosine triphosphate-dependent chromatin remodeling factors ISWI and DOM control germline stem cell and somatic stem cell self-renewal in the Drosophila ovary, respectively. The iswi mutant germline stem cells are lost rapidly because of defects in responding to bone morphogenetic protein niche signals and in repressing differentiation, whereas the dom mutant somatic stem cells are lost because of defective self-renewal. This work demonstrates that different stem cell types can use different chromatin remodeling factors to control cell self-renewal.     

垂丝海棠插穗扦插生根过程解剖学研究

从解剖学的角度观察垂丝海棠插穗不定根的发育过程,结果表明:垂丝海棠2年生插穗茎内无潜伏根原基,不定根由诱生根原基发育形成,诱生根源于愈伤组织自身形成的初生射线与维管形成层交汇处细胞的分裂分化。大约经40 d,不定根原基发育为幼小不定根并伸出周皮之外。并且愈伤组织内有些细胞分化为具螺纹加厚的厚壁细胞,在愈伤组织内产生根原基。     

美花石斛茎尖细胞分裂节律研究初报

采集不同季节、不同时间段的美花石斛茎尖,用品红染色,压片后显微观察,计算茎尖细胞的分裂指数。结果表明,美花石斛茎尖细胞的日分裂高峰为9：00（分裂指数3．3×10^-4）,月分裂高峰为5月。     

杜仲根组织分化的观察与分析

杜仲(Eucommia ulmoides Oliv.)的根为主根系。根尖顶端原始细胞分旱层为中柱原、皮层原和表皮-根冠原。整个根尖基本生长速率,自原始细胞向基端320μm前后最大,1200μm处下降到最小。原始细胞最初无分化,向基100μm处开始分化为初生分生组织,210μm处中柱鞘开始分化,500μm处出现最早筛管分子,620μm处出现最早导管分子,1300μm处表皮成熟形成根毛,2500μm处初生结构分化完成。内皮层凯氏带不明显,中柱鞘由一层细胞构成。木质部束多数为二原型,另外有三原、四原和五原型。韧皮部薄壁细胞形成许多橡胶丝。初生结构形成后,维管形成层即活动,产生次生维管组织,同时皮层第二层细胞分裂形成第一次的木栓形成层,产生周皮。次生韧皮部的轴向系统中也分化产生橡胶丝。侧根原基由木质部放射棱顶端中柱鞘细胞发生,根尖及成熟结构与主根相同。