Formation of a functional thymus initiated by a postnatal epithelial progenitor cell

The thymus is essential for the generation of self-tolerant effector and regulatory T cells. Intrathymic T-cell development requires an intact stromal microenvironment, of which thymic epithelial cells (TECs) constitute a major part. For instance, cell-autonomous genetic defects of forkhead box N1 (Foxn1) and autoimmune regulator (Aire) in thymic epithelial cells cause primary immunodeficiency and autoimmunity, respectively. During development, the thymic epithelial rudiment gives rise to two major compartments, the cortex and medulla. Cortical TECs positively select T cells, whereas medullary TECs are involved in negative selection of potentially autoreactive T cells. It has long been unclear whether these two morphologically and functionally distinct types of epithelial cells arise from a common bi-potent progenitor cell and whether such progenitors are still present in the postnatal period. Here, using in vivo cell lineage analysis in mice, we demonstrate the presence of a common progenitor of cortical and medullary TECs after birth. To probe the function of postnatal progenitors, a conditional mutant allele of Foxn1 was reverted to wild-type function in single epithelial cells in vivo. This led to the formation of small thymic lobules containing both cortical and medullary areas that supported normal thymopoiesis. Thus, single epithelial progenitor cells can give rise to a complete and functional thymic microenvironment, suggesting that cell-based therapies could be developed for thymus disorders.     

Distinct contribution of stem and progenitor cells to epidermal maintenance

The skin interfollicular epidermis (IFE) is the first barrier against the external environment and its maintenance is critical for survival. Two seemingly opposite theories have been proposed to explain IFE homeostasis. One posits that IFE is maintained by long-lived slow-cycling stem cells that give rise to transit-amplifying cell progeny, whereas the other suggests that homeostasis is achieved by a single committed progenitor population that balances stochastic fate. Here we probe the cellular heterogeneity within the IFE using two different inducible Cre recombinase–oestrogen receptor constructs targeting IFE progenitors in mice. Quantitative analysis of clonal fate data and proliferation dynamics demonstrate the existence of two distinct proliferative cell compartments arranged in a hierarchy involving slow-cycling stem cells and committed progenitor cells. After wounding, only stem cells contribute substantially to the repair and long-term regeneration of the tissue, whereas committed progenitor cells make a limited contribution.     

资产证券化带来的挑战

从金融管理者的角度研究了资产证券化的兴起会带来什么样的问题和挑战。     

Unique cell lines harbouring both Epstein-Barr virus and adult T-cell leukaemia virus, established from leukaemia patients

Members of three distinct classes of animal virus have been associated with naturally occurring neoplasias in man: Epstein--Barr virus (EBV), a DNA virus belonging to herpesvirus group, papillomavirus, and a novel human RNA (retro) virus, human T-cell leukemia virus or adult T-cell leukaemia (ATL) virus. We have established seven continuous cell lines from ATL patients and 0.1-7% of these cells consistently express ATL-specific antigens (ATLA). EBV-associated nuclear antigen (EBNA) is also found in more than 90% of these cells. We have cloned cells from two of these lines and show here that both ATLA and EBNA were present in the same B-cell clone carrying surface immunoglobulin (sIg).     

用JAVA实现MARC元数据向DC元数据的转换

概述了MARC元数据和DC元数据,分析了MARC向DC转换的必要性.同时利用现有的映射关系表,基于JAVA编程语言实现了MARC向DC的转换,演示了程序的运行过程并分析了转换程序的主要思路.     

由静态场到交变场的转变

不随时间变化的电荷所产生的静电场以及由传导电流所产生的恒流磁场属于静态场,而随时间变化的电荷以及传导电流就会产生交变场.这种变化的电场和磁场就不能通过静态场简单的规律来解释.麦克斯韦方程组是交变电磁场理论的核心.本文详细地介绍了麦克斯韦方程组的形成及推导,使读者能够轻松地完成从静态场到交变场的转变,并对交变电磁场理论有更深的理解.     

浅析从管理物业到经营物业

任何事物的产生,成长、壮大都要有一个艰难的过程,物业管理也不例外,目前,很多物业管理企业在生存、发展的过程中艰难经营,如何使企业走出困境,是广大物业人认真思考的问题,从经营角度上讲,要从管理物业向经营物业发展,在经营物业的过程中,实现投入、产出、利润的良性循环.     

从耗能建筑到节能建筑

文章通过8个建筑设计方案实例分析说明。耗能建筑涉及建筑设计思想．应引起社会各方面与建筑界的重视。建筑师以专业工作者身份参与组织社会生活。其建筑设计需以绿色建筑为设计理念,基于建筑节能。追求人与自然和谐、人与人和谐以及人自身和谐。     

Generation of a prostate from a single adult stem cell

The existence of prostate stem cells (PSCs) was first postulated from the observation that normal prostate regeneration can occur after repeated cycles of androgen deprivation and replacement in rodents. Given the critical role of PSCs in maintaining prostate tissue integrity and their potential involvement in prostate tumorigenesis, it is important to define specific markers for normal PSCs. Several cell-surface markers have been reported to identify candidate PSCs, including stem cell antigen-1 (Sca-1, also known as Ly6a), CD133 (Prom1) and CD44 (refs 3-10). However, many non-PSCs in the mouse prostate also express these markers and thus identification of a more defined PSC population remains elusive. Here we identify CD117 (c-kit, stem cell factor receptor) as a new marker of a rare adult mouse PSC population, and demonstrate that a single stem cell defined by the phenotype Lin(-)Sca-1(+)CD133(+)CD44(+)CD117(+) can generate a prostate after transplantation in vivo. CD117 expression is predominantly localized to the region of the mouse prostate proximal to the urethra and is upregulated after castration-induced prostate involution-two characteristics consistent with that of a PSC marker. CD117(+) PSCs can generate functional, secretion-producing prostates when transplanted in vivo. Moreover, CD117(+) PSCs have long-term self-renewal capacity, as evidenced by serial isolation and transplantation in vivo. Our data establish that single cells in the adult mouse prostate with multipotent, self-renewal capacity are defined by a Lin(-)Sca-1(+)CD133(+)CD44(+)CD117(+) phenotype.     

抽象论域到数据结构的转换

给出了函数式语言到过程式语言转换的关键技术,即抽象论域到具体数据结构的转换技术.抽象论域的转换是抽象表达式到具体表达式转换、模式匹配处理的前提.函数式语言到过程式语言的转换,解决了函数式语言在具体实现和时间方面存在的大量动态函数复制的问题.这种转换技术可用于开发指称语义到解释器、指称语义到编译器、属性文法到过程式语言、属性文法到YACC(Yet Another Computer Compilier)输入文件的各种自动生成器.     

Transformation of cell adhesion properties by exogenously introduced E-cadherin cDNA

E-cadherin is a cell surface glycoprotein responsible for Ca2+-dependent intercellular adhesion between epithelial cells; it is also called uvomorulin, L-CAM (ref. 3), cell-CAM 120/80 (ref.4) or Arc-1 (ref. 5). Because blocking the action of E-cadherin by monoclonal antibodies causes dispersion of compact cell colonies, this molecule is thought to be an important factor for maintenance of multicellular systems. To demonstrate directly that E-cadherin is involved in cell-cell adhesion, we cloned full-length cDNA encoding E-cadherin from F9 cells and introduced it into L fibroblasts deficient in E-cadherin. These L cells acquire strong Ca2+-dependent aggregating activity by expressing the E-cadherin derived from the introduced cDNA and were morphologically transformed so as to form colonies in which cells were tightly connected to each other.     

保序部分单变换半群到保序部分变换半群的同态

设 IOn和POn分别是集合X n＝｛1,2,…,n｝上的保序部分单变换半群和保序部分变换半群。文章刻画了 I On到 PO n的所有同态。