Noggin与成体神经发生的调控

神经干细胞存在于中枢神经系统的广泛区域,且这些细胞具有分化为神经元的潜能。noggin通过拮抗内源性骨形态蛋白(Bone Morphological Prote in,BMPs)的作用促进生理状态下成年动物室下区和海马齿状回成体神经元发生。并且noggin参与中枢神经系统损伤和退行性疾病等病理状态下神经发生的过程,外源性noggin可以促进中枢神经系统功能恢复。     

Molecular Mechanisms Controlling the Cell Cycle in Embryonic Stem Cells

Embryonic stem (ES) cells are originated from the inner cell mass of a blastocyst stage embryo. They can proliferate indefinitely, maintain an undifferentiated state (self-renewal), and differentiate into any cell type (pluripotency). ES cells have an unusual cell cycle structure, consists mainly of S phase cells, a short G1 phase and absence of G1/S checkpoint. Cell division and cell cycle progression are controlled by mechanisms ensuring the accurate transmission of genetic information from generation to generation. Therefore, control of cell cycle is a complicated process, involving several signaling pathways. Although great progress has been made on the molecular mechanisms involved in the regulation of ES cell cycle, many regulatory mechanisms remain unknown. This review summarizes the current knowledge about the molecular mechanisms regulating the cell cycle of ES cells and describes the relationship existing between cell cycle progression and the self-renewal.     

Neurogenesis in the Adult Goldfish Cerebellum

Neurogenesis was studied in the cerebellum of adult goldfish, to establish the phenomenon in this popular laboratory animal model. BrdU and proliferating cell nuclear antigen labeling revealed a high rate of cell proliferation within the molecular layer of the cerebellar corpus and valve. Most newborn cells expressed the neuronal marker beta‐III‐tubulin after 24 hr, supporting the goldfish cerebellum as an excellent paradigm to study vertebrate adult neurogenesis. Anat Rec, 2010. © 2010 Wiley‐Liss, Inc.     

Cell Cycle Regulation and Differentiation in the Human Podocyte Lineage

Mature podocytes are regarded as growth-arrested cells with characteristic phenotypic features that underlie their function. To determine the relationship between cell cycle regulation and differentiation, the spatiotemporal expression of cyclin A, cyclin B1, cyclin D1, the cyclin-dependent kinase inhibitors (CKIs) p27 and p57, and markers of differentiating podocytes in developing human kidneys was investigated by immunohistochemistry. In S-shaped body stage, Ki-67, a cell proliferation marker that labels the G1/S/G2/M phase, was expressed in the majority (more than 80%) of presumptive podocytes, along with cyclin A (~20% of the Ki-67-positive cells) and cyclin B1 (less than 5% of Ki-67-positive cells) expression. Among these cells, cyclin D1 and CKIs were markedly down-regulated. At the capillary-loop stage, by contrast, CKIs and cyclin D1 were intensely positive in podocytes, whereas no Ki-67, cyclin B1, or cyclin A expression was seen. Moreover, double-immunolabeling and serial-section analysis provided evidence that CKIs and markers specific for differentiating podocytes, namely PHM-5 (podocalyxin-like protein in humans), synaptopodin (a foot process-related protein), and C3b receptor, were co-expressed at the capillary-loop stage. Podocytes were the only cells within the glomeruli that expressed CKIs at immunohistochemically detectable levels. Furthermore, bcl-2 (an apoptosis inhibitory protein) showed a reciprocal expression pattern to that of CKI. These results suggest that 1) the cell cycle of podocytes is regulated by cyclin and CKIs, 2) CKIs may act to arrest the cell cycle in podocytes at the capillary-loop stage, and 3) the specific cell cycle system in podocytes may be closely correlated with their terminal differentiation in humans.     

人牙髓细胞向成牙本质细胞诱导分化中细胞周期变化

目的建立成牙本质细胞样细胞体外培养体系，观察体外培养的牙髓细胞向成牙本质细胞分化过程中细胞周期的变化。方法利用组织块酶解法培养人牙髓细胞并进行鉴定，使用矿化诱导液诱导其向成牙本质细胞样细胞分化。对细胞增殖情况使用流式细胞仪进行细胞周期测定。结果①获得的牙髓细胞均为波形丝蛋白阳性，角蛋白阴性，证明为中胚层来源的细胞。②诱导分化的牙髓细胞在2周左右进入复层生长期；3周左右开始有细胞结节形成．周围细胞呈放射状排列，部分细胞出现细长突起并呈极性排列：4周左右细胞团中央Von Kossa染色为阳性。③在诱导开始后1周，细胞处于活跃的增殖期，以后细胞增殖变慢．3周后多数细胞处于G0G1期。结论实验成功建立了成牙本质细胞样细胞体外培养体系，所获得的成牙本质细胞样细胞具有成牙本质细胞的部分形态和生物学功能，诱导分化后细胞增殖变慢．是研究成牙本质细胞的较好模型。     

Synthesis and Expression of Surface Antigens During the Cell Cycle

The expression of H–2 histocompatibility antigens, assayed by immune cytolysis, is minimal during the S period of the cell cycle. In order to investigate this phenomenon, we have measured the amount of H–2 antigens on P815Y cells at different stages of the cell cycle by two different techniques. The first involves the binding of [¹²⁵I] labelled antibody, the second the inhibition of immune cytolysis of indicator cells by bound and salt-extractable antigens.
Each method shows that the amount of H–2 antigens increases during the G₁ period and then remains constant. On the other hand, the fragility of cells assayed by cytolysis caused by detergents, hypotonicity or freeze thawing shows the same minimum in S as does the expression of H–2 measured by immune cytolysis.
It is concluded that cell surface antigens are inserted into the plasma membrane during G₁ and remain accessible to combination with antibody thereafter. Because of a decrease in cellular fragility during interphase, cytolytic techniques should be used with caution.     

Expansion of the Human Embryonic Brain During Rapid Growth: Area Analysis

This report focuses on growth of the brain of the early human embryo, Carnegie stages 12–23. Areas of median sections from 50 to 58 embryos were measured to determine the best mathematical model to describe growth of the three primary brain vesicles and to determine the change in the ratio of tissue to cavity areas (T/C). An exponential model best describes growth of the brain and head during this time period. The head expands 248‐fold compared with a 171‐fold growth of the brain. The whole brain, forebrain, and midbrain all exhibit larger cavities than tissue initially followed by a reversal of such at a critical time (stages 21–24). The presumptive cerebellar tissue which was twice the cavity initially grows to become more than six times the cavity. Boxplots of the T/C ratios for the head and brain plus its components reveal that initially the tissue is less than the cavity (10–20% and 40–60%, respectively) but eventually becomes larger (60–200%). Anat Rec, 292:472–480, 2009. © 2009 Wiley‐Liss, Inc.     

Individual Peculiarities of the Development and Differentiation of Embryonic Neocortex Transplants in Intact Adult Mouse Brain

Bulletin of Experimental Biology and Medicine - We studied individual peculiarities of the development and differentiation of allogeneic transplants of neocortical cells isolated from embryos at...     

Structure of Cell Clusters Formed in Cultures of Dissociated Human Embryonic Brain

Cell clusters in a culture of dissociated brain from human fetuses at 8-12 weeks gestation in a serum-free growth medium were studied by immunohistochemical methods and electron microscopy. Heterogeneity of cell population in culture was demonstrated. Despite the influence of proliferation-stimulating factors, cell clusters contained not only nestin-immunopositive stem cells, but also b-tubulin-, vimentin-, and GFAP-positive cells differentiating by the neural pathway. Stem cells were localized on the surface of clusters. The percentage of stem cells in large clusters was lower than in small clusters.     

纺锤体检测点机制对细胞周期的调控

细胞周期的各个步骤是连续进行的,各个步骤都受到严格而精细的调控,在某一个环节出现错误将会妨碍后续过程的进行,进而出现细胞分裂错误而导致非整倍体细胞,肿瘤细胞形成或细胞死亡。有丝分裂的后期染色体分离到两个子代细胞中,只有染色体平均分配到子代细胞中才能保证遗传的稳定性,但细胞分裂是一个不可逆的过程,所以染色体的分离是细胞分裂最为重要的一个步骤,这一步骤受到一种称为纺锤体监测点（spindle checkpoint,SCP)机制的严格调控。这种机制在纺锤体组装出现错误时或染色体与微管连接出现错误时就会激活,激活后对细胞周期发出一个阻碍信号进而影响两个主要的细胞周期过程①只有两个染色单体与来自两极的微管形成稳定而且正确的连接后,后期才开始进行;②直到姊妹染色单体正确的分离后有丝分裂才结束。本文主要是介绍SCP对前一个过程的调控作用。     

Changes in the Distribution of Cell Contacts and Mitotic Cycle Disturbances in Cells of the Allograft of Rat Embryonic Neocortex

Bulletin of Experimental Biology and Medicine - Morphological changes in the allograft of rat anterior cerebral vesicle at the early stages after transplantation into the peripheral nerve of an...     

人胚胎期心脏蒲肯野细胞结构的光镜和电镜研究

为了揭示人胚胎期蒲肯野细胞的形态学构筑 ,本实验选用医院水囊引产发育正常胎儿 6例 ,固定后取包含有心内膜的左心室心肌组织 ,分别采用普通光镜、扫描电镜化学消化法和镀银染色方法对心脏传导系统蒲肯野细胞的形态及立体构筑进行研究。结果表明人胚胎期蒲肯野细胞为椭圆形 ,直径较普通心肌细胞大 2倍左右 ,闰盘复杂 ,细胞周围有明显的网状纤维鞘。蒲肯野细胞的上述构象有利于冲动沿细胞单一方向快速传导。     

Adenosine Deaminase Activity During the Growth Cycle of T and B Lymphoid Cell Lines

Adenosine deaminase activity per cell was constant during the growth of B cells but increased during logarithmic growth of T cells and decreased as T cell viability decreased during the stationary phase of growth. This elevated enzyme activity appears to be a biochemical marker for T cell leukemic blasts.     

应用流式细胞术分析不同年龄大鼠脑组织细胞周期增殖特性

应用流式细胞术对不同年龄的大鼠的大脑、小脑和脑干组织的细胞周期进行分析。结果显示在相同年龄组不同部位的脑组织细胞增殖程度不均一,大脑细胞增殖明显高于小脑和脑干。同一部位的脑组织各年龄组之间细胞增殖情况亦存在差异。新生和幼年大鼠(出生后1天和21天)其脑细胞增殖较成年大鼠(6个月和1年)旺盛。实验还表明,特殊萤光素染色脑细胞DNA,然后用流式细胞仪测定DNA量,是一种简单、快速分析脑细胞增殖活性的可行技术。