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21.
Temporal lobe epilepsy (TLE) is the most frequent form of epilepsy in adults. In addition to recurrent focal seizures, patients suffer from memory loss and depression. The factors contributing to these symptoms are unknown. In recent years, adult hippocampal neurogenesis has been implicated in certain aspects of learning and memory, as well as in depression and anhedonia. Here we investigated whether the adult hippocampal stem cell niche is affected by status epilepticus in a mouse model of TLE using unilateral intrahippocampal kainic acid injection. Eight days after status epilepticus, we found a strong diminution in Notch signalling, a key pathway involved in stem cell maintenance, as assayed by hes5 reporter gene activity. In particular, hes5–GFP expression in the subgranular zone of the dentate gyrus was diminished. Furthermore, Sox2‐positive cells as well as stem cell proliferation were reduced, thus pointing to a disruption of the stem cell niche in epilepsy under the present experimental conditions.  相似文献   
22.
背景:细胞外基质是组织微环境的重要组分,为维持细胞功能提供了关键的生化和物理信号。 目的:对体外模拟骨髓干细胞微环境的研究进展进行综述,着重于介绍体外再造细胞外基质。 方法:应用计算机检索Pubmed (1999-01/2010-10)、Embase (1999-01/2010-10)数据库中关于干细胞微环境的文章,以“mesenchymal stem cells; extracellular matrix; niche; growth factor modulation; culture in vitro”为检索词进行检索。初检得到321篇文献,根据纳入标准选择关于干细胞微环境的23篇文献进行综述。 结果与结论:骨髓源性的细胞外基质培养体系能保持间充质干细胞的特性,对纯化这些细胞和形成更多数量的同质间充质干细胞提供了便利。使用3D合成材料建立一个独特的骨架,包被组织特异性的间充质干细胞蛋白,并添加正确的生长因子组合,有利于调控间充质干细胞的分化方向。  相似文献   
23.
Cancer stem cells are thought to be closely related to tumor progression and recurrence, making them attractive therapeutic targets. Stem cells of various tissues exist within niches maintaining their stemness. Glioblastoma stem cells (GSCs) are located at tumor capillaries and the perivascular niche, which are considered to have an important role in maintaining GSCs. There were some extracellular matrices (ECM) on the perivascular connective tissue, including type 1 collagen. We here evaluated whether type 1 collagen has a potential niche for GSCs. Imunohistochemical staining of type 1 collagen and CD133, one of the GSCs markers, on glioblastoma (GBM) tissues showed CD133‐positive cells were located in immediate proximity to type 1 collagen around tumor vessels. We cultured human GBM cell lines, U87MG and GBM cells obtained from fresh surgical tissues, T472 and T555, with serum‐containing medium (SCM) or serum‐free medium with some growth factors (SFM) and in non‐coated (Non‐coat) or type 1 collagen‐coated plates (Col). The RNA expression levels of CD133 and Nestin as stem cell markers in each condition were examined. The Col condition not only with SFM but SCM made GBM cells more enhanced in RNA expression of CD133, compared to Non‐coat/SCM. Semi‐quantitative measurement of CD133‐positive cells by immunocytochemistry showed a statistically significant increase of CD133‐positive cells in Col/SFM. In addition, T472 cell line cultured in the Col/SFM had capabilities of sphere formation and tumorigenesis. Type 1 collagen was found in the perivascular area and showed a possibility to maintain GSCs. These findings suggest that type 1 collagen could be one important niche component for CD133‐positive GSCs and maintain GSCs in adherent culture.  相似文献   
24.
一个多世纪前Paget就肿瘤器官特异性转移现象提出了“种子与土壤”学说。时下研究热点集中在一些特殊因子介导的靶器官环境改造,肿瘤细胞归巢行为。有动物实验证实肺转移瘤形成前,肺部已发生大量炎症因子聚集。宿主靶器官的改变影响转移瘤形成的每一个步骤。BethanPsaila与DavidLyden针对这一土壤变化过程提出转移前微环境(pre-metastaticniche)及转移微环境(metastaticniche)假说,指出土壤的变化是转移瘤形成的保障。该假说提出后迅速引起肿瘤研究界轰动。研究这一系列细胞分子生物学的改变,有助于阐明肿瘤转移这一复杂的过程,为转移干预带来新的思路。  相似文献   
25.
The pharmaceutical industry can be divided into a top tier of about 30 major league companies and a second tier (minor league) comprising several thousand. This paper focused on the second tier and the particular challenge of minor league companies—especially niche players—to balance operating requirements and strategic ambitions within limited and limiting resources. In the authors' experience, survival as a niche player requires not only that the company stays on the technology frontier but also that risk willingness and innovative behavior be characteristic of managers' mindset. To this end, the authors share 13 “ground rules” to perform appropriately as a niche player. © 1993 wiley-Liss, Inc.  相似文献   
26.
PurposeLimbal niche cells (LNCs) play a vital role in the maintenance of limbal epithelial stem/progenitor cells (LESCs). Four methods have been reported to isolate and expand LNCs: digestion by collagenase alone (C-LNC), collagenase following dispase removal of the limbal epithelium (DC-LNC), dissection of dispase-isolated limbal epithelial sheets (D-LNC), and explant cultures of limbal stromal tissues (Ex-LNC). This study aimed to isolate LNCs using those four methods and to compare their capacity to maintain LESCs.MethodsLNCs were isolated from the rat corneal limbus by the following methods: C-LNC, DC-LNC, D-LNC, and Ex-LNC. Quantitative real-time PCR and immunofluorescence staining were used to analyze the expression of embryonic stem cell (ESC) markers. The ability to maintain LESCs was assessed on the basis of colony-forming capacity and the expression of progenitor, proliferation, and differentiation markers in three-dimensional (3D) Matrigel and Transwell systems. Notch signaling of LESCs supported by different LNCs in Transwell inserts was analyzed by quantitative real-time PCR.ResultsDC-LNCs exhibited lower expression of CK12 during isolation and expansion. Among P4-expanded LNCs, DC-LNCs expressed significantly higher levels of Sox2, Oct4, Nanog, and N-cadherin than C-LNCs, D-LNCs, and Ex-LNCs. Compared with other LNCs, DC-LNCs were more effective in maintaining LESCs with higher holoclone-forming efficiency, greater expression of ΔNp63α and Ki67, and lower expression of CK12. DC-LNCs were also more capable of downregulating Notch signaling of LESCs.ConclusionsDC-LNCs were more effective in expressing ESC markers and maintaining LESCs compared to other LNCs. This study identifies an optimal method for the isolation of LNCs in tissue engineering and ocular surface reconstruction.  相似文献   
27.
目的 研究中国鼠疫自然疫源地的形成、起源、演化动态与环境生态位生物学基本规律,揭示中国鼠疫自然疫源地的形成环境,确定中国鼠疫自然疫源地的起源、演化动态标准.方法 采用之前研究中提出的中国鼠疫自然疫源地分型方法,综合研究中国鼠疫生态地理景观型分型法、中国鼠疫耶尔森菌(鼠疫菌)基因组型分型法、鼠疫菌生物型分型法和中国鼠疫主要宿主、主要媒介的物种分类和地理空间分布.结果 综合上述鼠疫自然疫源地中的多因子,提出中国鼠疫自然疫源地演化动态的理论结果,中国鼠疫自然疫源地最早起源于天山森林草原灰旱獭、长尾黄鼠鼠疫自然疫源地型.中国鼠疫自然疫源地型均起源于该疫源地型.结论 中国鼠疫自然疫源地最早起源于天山灰旱獭、长尾黄鼠森林草原鼠疫自然疫源地.  相似文献   
28.
The purpose of this study has been to explore young children's understandings and experiences of friendship as these manifested in children's behaviours, in a reception class setting. Drawing on an evolutionary, ecological framework, friendship is seen as not only the expression and further development of social understandings and cognitive advances; more than that, making and maintaining friends is seen as an evolutionary trait and a ‘drive’ to relate to similarly minded others. Through ‘niche picking’, children select the environments and opportunities that suit them in order to develop their dispositions and individual traits. The research employed a participatory design in order to capture the children's views and experiences. It took place in a reception class setting, where children's everyday experiences were observed and discussed with them. The study identified six themes of analysis and offered some suggestions about creating enabling educational environments that allow the ‘space’ for niche construction.  相似文献   
29.
目的 探讨采用空间信息技术及生态位理论预测新疆准噶尔盆地大沙鼠的适生区分布,提高鼠疫监测效率.方法 通过现场调查获得准噶尔盆地大沙鼠分布的全球定位系统经纬度信息,通过遥感获得环境变量图层,利用Maxent软件建模,结合地理信息系统获得大沙鼠适生区分布图,对模型评价并划分风险分级图,叠加人口数据标示重点关注地区.结果 模型预测精度较高,曲线下面积值为0.968,灵敏度为91.4%,特异度为63.3%,准确度为73.8%,阳性预测值为59.7%,阴性预测值为92.6%,Kappa系数为0.495.大沙鼠适生区分布在准噶尔盆地及其周边大部分区县,高风险地区总面积约37 304 km2,约占总面积的6.2%,主要分布在昌吉回族自治州、乌鲁木齐市米东区及克拉玛依市,其中米东区、克拉玛依市辖区及乌尔禾区的分布较广;区域内人口约12万,分布于261 km2区域内.重点监测地区包括乌鲁木齐市、五家渠市、克拉玛依市、博乐市、精河县、奎屯市、阜康市、吉木萨尔县及木垒哈萨克自治县.结论 生态位理论和遥感环境数据可预测新疆准噶尔盆地大沙鼠潜在适生区,并显著缩小了重点监测的靶地区.  相似文献   
30.
Identification of human monkeypox cases during 2005 in southern Sudan (now South Sudan) raised several questions about the natural history of monkeypox virus (MPXV) in Africa. The outbreak area, characterized by seasonally dry riverine grasslands, is not identified as environmentally suitable for MPXV transmission. We examined possible origins of this outbreak by performing phylogenetic analysis of genome sequences of MPXV isolates from the outbreak in Sudan and from differing localities. We also compared the environmental suitability of study localities for monkeypox transmission. Phylogenetically, the viruses isolated from Sudan outbreak specimens belong to a clade identified in the Congo Basin. This finding, added to the political instability of the area during the time of the outbreak, supports the hypothesis of importation by infected animals or humans entering Sudan from the Congo Basin, and person-to-person transmission of virus, rather than transmission of indigenous virus from infected animals to humans.  相似文献   
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