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<正>Since the first murine and human embryonic stem cell lines were established by Drs. Evans and Kaufman [1] and Thomson et al. [2], respectively, great progress has been make in the field of  相似文献   

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Mammalian Müller cells have been reported to possess retinal progenitor cell properties and generate new neurons after injury. This study investigates murine Müller cells under in vitro conditions for their capability of dedifferentiation into retinal progenitor cells. Müller cells were isolated from mouse retina, and proliferating cells were expanded in serum-containing medium. For dedifferentiation, the cultured cells were transferred to serum-replacement medium (SRM) at different points in time after their isolation. Interestingly, early cell passages produced fibrous tissue in which extracellular matrix proteins and connective tissue markers were differentially expressed. In contrast, aged Müller cell cultures formed neurospheres in SRM that are characteristic for neuronal progenitor cells. These neurospheres differentiated into neuron-like cells after cultivation on laminin/ornithine cell culture substrate. Here, we report for the first time that murine Müller cells can be progenitors for both, fibrous tissue cells and neuronal cells, depending on the age of the cell culture.  相似文献   

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Glial cells are the most abundant cells in the human brain and have long been considered as passive supporting cells for neurons. In contrast to the extensive studies on various neuronal functions in the nervous system, we still have limited knowledge about glial cells. Recently a number of pioneering studies have provided convincing evidence that glia play active roles in development and function of the central nervous system. This review discusses recent advances in our understanding of the molecular mechanisms underlying glial cell differentiation. We then highlight some of the novel findings about glial function, i.e. the role of glia in synaptogenesis and the intricate relationship between astrocytes and adult neural stem cells. Finally, we summarize the emerging studies that implicate abnormalities in the formation or maintenance of glia leading to severe brain diseases, such as Alexander disease, glioblastoma and multiple sclerosis, and potential therapeutic strategies to tackle these diseases.  相似文献   

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Mesenchymal stromal cells (MSCs) are considered to be promising agents for the treatment of immunological disease. Although originally identified as precursor cells for mesenchymal lineages, in vitro studies have demonstrated that MSCs possess diverse immune regulatory capacities. Pre-clinical models have shown beneficial effects of MSCs in multiple immunological diseases and a number of phase 1/2 clinical trials carried out so far have reported signs of immune modulation after MSC infusion. These data indicate that MSCs play a central role in the immune response. This raises the academic question whether MSCs are immune cells or whether they are tissue precursor cells with immunoregulatory capacity. Correct understanding of the immunological properties and origin of MSCs will aid in the appropriate and safe use of the cells for clinical therapy. In this review the whole spectrum of immunological properties of MSCs is discussed with the aim of determining the position of MSCs in the immune system.  相似文献   

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The sinoatrial node(SAN)is the headquarter of heartbeat throughout our lifetime(Lakatta et al.,2010;Cingolani et al.,2018;Peters et al.,2020).Every beat of the heart is triggered by a bioelectric pulse spontaneously released by SAN pacemaker cells(SANPCs)(Yaniv et al.,2014;Yavari et al.,2017).In adult human heart,the SAN is a crescent-shaped structure of 1-2 cm long and 0.5 cm wide,which is located at the junction of the superior vena cava and the right atrium and lies along the sulcus terminalis(John et al.,2016).However,the nature of SANPCs remains incompletely known.In general,SANPCs have long been considered as specialized cardiomyocytes(Van Eif et al.,2018;Linscheid et al.,2019;Galang et al.,2020;).However,SANPCs do not have myofibril and T-tube,thus not sharing the contractility property of cardiomyocytes(Satoh,2003;Protze et al.,2017).Interestingly,SANPCs share some electrophysiolog-ical characteristics with neurons:excitability and conductiv-ity.In addition,SANPCs have their intrinsic autonomic rhythm,while neurons also possess the intrinsic ability to generate spontaneous electrical impulses(Lisman et al.,2018).Whether SANPCs are neuron-like cells that reside in the heart remains enigmatic in the field.  相似文献   

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Folliculo-stellate cells (FS-cells) in the anterior pituitary gland are star-shaped cells and form tiny follicles. FS-cells are positive for S-100 protein and produce many cytokines or growth factors, such as interleukin-6 (IL-6), leukemia inhibitory factor (LIF), basic fibroblastic growth factor (bFGF) and vascular endothelial cell growth factor (VEGF). Therefore, it is generally accepted that FS-cells regulate endocrine cells through these growth factors. FS-cells also exhibit a phagocytotic activity and are known to work as scavenger cells. In addition to these functions, FS-cells are considered to have some unknown functions. In order to reveal the biological significance of FS-cells in the anterior pituitary gland, we performed a morphological study and obtained some new findings. First, we were interested in the colloid formation in the senescent porcine pituitary gland. We analyzed the colloids and found that clusterin is a major protein in them. We also found that the accumulation of clusterin in the colloids is related to the phagocytotic activity of FS-cells. In our next study, we found that FS-cells have the potential to differentiate into striated muscle cells. From FS-cells show multi-potent cell character and other cytological evidence, we propose that FS-cells are candidate of organ-specific stem cells in the anterior pituitary gland.  相似文献   

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Summary Lymphapheresis was performed on a patient with Sézary syndrome. The Sézary cells were purified by removing E-rosette-forming and Fc receptor-bearing cells. Antiserum against these purified Sézary cells was raised in rabbits. This antiserum had cytotoxicity against Sézary cells as well as against normal peripheral blood lymphocytes. Absorption was carried out with chronic lymphocytic leukemia (CLL) and normal lymphocytes. The absorbed antiserum maintained cytotoxicity against Sézary cells but lost cytotoxicity against CLL and normal peripheral blood lymphocytes.Indirect immunofluorescence assay showed that the antiserum reacted against purified Sézary cells and a high percentage (66%) of peripheral blood mononuclear cells from five patients with Sézary syndrome. It also reacted against 5.7% of normal lymphocytes, 8% of CLL cells, 5% of the lymphocytes from a patient who had undergone splenectomy, 2% of lymphocytes from a patient with multiple myeloma, 5% of lymphocytes from a hairy cell leukemia patient, and 1% of acute lymphocytic leukemia cells (T cell). The antiserum did not react against thymocytes but reacted against 34.6% of the bone marrow lymphocytes. This unique marker was designated as sigma () antigen. It was suggested that Sézary syndrome may represent proliferation or malignant transformation of normally present antigen-positive lymphocytes.  相似文献   

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Developmental potency of primitive and embryonic ectoderm cells from 4.50-day to 6.25-day post-coitum (p.c.) mouse embryos and primordial germ cells from 12.50-day p.c.male genital ridges of fetal mice were studied by direct introducing them into 3.50-day p.c.blastocysts.Sixteen (61.5) overt chimaeras out of 26(50%) offsprings were obtained after transfer of 52 blastocysts injected with 4.50-day primitive ectoderm cells;four (16.0%) overt chimaeras were obtained out of 25 (51.0%) offsprings with 4.75-day primitive ectoderm cells from 49 transferred blastocysts.However,no overt chimaera was obtained with either 5.25-day or 6.25-day embryonic ectoderm cells or 12.50-day male primordial germ cells.GPI analysis of mid-gestation conceptuses developed from injected blastocysts showedthat 5.25-day embryonic ectoderm cells could only contributed to yolk sac of conceptus.Results suggested that implantation acts as a trigger for the determination of primitive ectoderm cells,and their developmental potency becomes limited within a short period of time in normal development.  相似文献   

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Understanding life supposes that one will,one day,reconstruct cells. A deep analysis of what life is shows that a cell is similar to a computers making computer. This asks for several orginal levels of organisation. First,the cell needs to be seen as a machine separated from the genetic program,which it runs. Over generations the machine reproduces,while the program replicates. Reproduction is a process which is able to accumulate valuable information over generations. Extracting valuable information from an ocean of noise requires an energy-dependent process which uses energy to prevent degradation of functional entities. Analysis of bacterial genomes shows that the core set of genes which persist in most genomes code for the functions needed to perform this process of ratchet-like information accumulation. It also suggests that a mineral,polyphosphates,could be a ubiquitous (and stable) energy source essential for the process.  相似文献   

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Peroxisome proliferator activated receptor γ, belongs to PPARs, which exerts various metabolic functions including differentiation process. To testify the importance of PPARγ in neural differentiation of mouse embryonic stem cells (mESCs), its expression level was assessed. Data revealed an elevation in expression level of PPARγ when neural precursors (NPs) are formed upon retinoic acid treatment. Thus, involvement of PPARγ in two stages of neural differentiation of mESCs, during and post-NPs formation was examined by application of its agonist and antagonist. Our results indicated that PPARγ inactivation via treatment with GW9662 during NPs formation, reduced expression of neural precursor and neural (neuronal and astrocytes) markers. However, PPARγ inactivation by antagonist treatment post-NPs formation stage only decreased the expression of mature astrocyte marker (Gfap) suggesting that inactivation of PPARγ by antagonist decreased astrocyte differentiation. Here, we have demonstrated the stage dependent role of PPARγ modulation on neural differentiation of mESCs by retinoic acid treatment for the first time.  相似文献   

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Can resting B cells present antigen to T cells?   总被引:3,自引:0,他引:3  
Antigen stimulation of T lymphocytes can occur only in the presence of an antigen-presenting cell (APC). An ever-increasing number of cell types have been found to act as APCs; these include macrophages, splenic and lymph node dendritic cells, and Langerhans' cells of the skin. Although activated B lymphocytes and B cell lymphomas are known to serve as APCs, it has been generally believed that resting B cells cannot perform this function. However, in recent studies we have found that resting B cells can indeed present soluble antigen to T cell clones as well as to antigen-primed T cells. The previous difficulty in demonstrating this activity can be explained by the finding that, in contrast to macrophages and dendritic cells, the antigen-presenting ability of resting B cells is very radiosensitive. Macrophages are usually irradiated with 2000-3300 rads to prevent them from incorporating [3H]thymidine in the T cell proliferation assay. Resting B cells, however, begin to lose presenting function at 1500 rads and have completely lost this activity at 3300 rads. It was also possible to distinguish two distinct T cell clonal phenotypes when resting B cells were used as APCs on the basis of two different assays (T cell proliferation, and B cell proliferation resulting from T cell activation). The majority of T cell clones tested were capable of both proliferating themselves and inducing the proliferation of B cells. Some T cells clones, however, could not proliferate in the presence of antigen and B cell APCs, although they were very good at inducing the proliferation of B cells. This suggests that there are two distinct pathways of T cell activation, one leading to T cell proliferation and the other leading only to the release of lymphokines (as measured by the polyclonal activation of B cells).  相似文献   

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Isolation of epithelial cells for cell culture is based on destruction of epithelial integrity. The consequences are manifold: cell polarity and specific cell functions are lost; cells acquire non‐epithelial characteristics and start to proliferate. This situation may also occur in situ when parts of the epithelium are lost, either by apoptosis or necrosis by organ or tissue injury. During recovery from this injury, surviving epithelial cells proliferate and may restore epithelial integrity and finally re‐differentiate into functional epithelial cells. In vitro, this re‐differentiation is mostly not complete due to sub‐optimal culture conditions. Therefore cultured epithelial cells resemble wounded or injured epithelia rather than healthy and well differentiated epithelia. The value of an in vitro cell model is the extent to which it helps to understand the function of the cells in situ. A variety of parameters influence the state of differentiation of cultured cells in vitro. Although each of these parameters had been studied, the picture how they co‐ordinately influence the state of differentiation of epithelial cells in vitro is incomplete. Therefore we discuss the influence of the isolation method and cell culture on epithelial cells, and outline strategies to achieve highly differentiated epithelial cells for the use as an in vitro model.  相似文献   

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