共查询到20条相似文献，搜索用时 31 毫秒
1.
Kierzkowski D Nakayama N Routier-Kierzkowska AL Weber A Bayer E Schorderet M Reinhardt D Kuhlemeier C Smith RS 《Science (New York, N.Y.)》2012,335(6072):1096-1099
Although genetic control of morphogenesis is well established, elaboration of complex shapes requires changes in the mechanical properties of cells. In plants, the first visible sign of leaf formation is a bulge on the flank of the shoot apical meristem. Bulging results from local relaxation of cell walls, which causes them to yield to internal hydrostatic pressure. By manipulation of tissue tension in combination with quantitative live imaging and finite-element modeling, we found that the slow-growing area at the shoot tip is substantially strain-stiffened compared with surrounding fast-growing tissue. We propose that strain stiffening limits growth, restricts organ bulging, and contributes to the meristem's functional zonation. Thus, mechanical signals are not just passive readouts of gene action but feed back on morphogenesis. 相似文献
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The atypical cadherin Fat acts as a receptor for a signaling pathway that regulates growth, gene expression, and planar cell polarity. Genetic studies in Drosophila identified the four-jointed gene as a regulator of Fat signaling. We show that four-jointed encodes a protein kinase that phosphorylates serine or threonine residues within extracellular cadherin domains of Fat and its transmembrane ligand, Dachsous. Four-jointed functions in the Golgi and is the first molecularly defined kinase that phosphorylates protein domains destined to be extracellular. An acidic sequence motif (Asp-Asn-Glu) within Four-jointed was essential for its kinase activity in vitro and for its biological activity in vivo. Our results indicate that Four-jointed regulates Fat signaling by phosphorylating cadherin domains of Fat and Dachsous as they transit through the Golgi. 相似文献
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Toyama Y Peralta XG Wells AR Kiehart DP Edwards GS 《Science (New York, N.Y.)》2008,321(5896):1683-1686
Understanding cell morphogenesis during metazoan development requires knowledge of how cells and the extracellular matrix produce and respond to forces. We investigated how apoptosis, which remodels tissue by eliminating supernumerary cells, also contributes forces to a tissue (the amnioserosa) that promotes cell-sheet fusion (dorsal closure) in the Drosophila embryo. We showed that expression in the amnioserosa of proteins that suppress or enhance apoptosis slows or speeds dorsal closure, respectively. These changes correlate with the forces produced by the amnioserosa and the rate of seam formation between the cell sheets (zipping), key processes that contribute to closure. This apoptotic force is used by the embryo to drive cell-sheet movements during development, a role not classically attributed to apoptosis. 相似文献
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During animal development, epithelial cell fates are specified according to spatial position by extracellular signaling pathways. Among these, the transforming growth factor beta/bone morphogenetic protein (TGF-beta/BMP) pathways are evolutionarily conserved and play crucial roles in the development and homeostasis of a wide range of multicellular tissues. Here we show that in the developing Drosophila wing imaginal epithelium, cell clones deprived of the BMP-like ligand Decapentaplegic (DPP) do not die as previously thought but rather extrude from the cell layer as viable cysts exhibiting marked abnormalities in cell shape and cytoskeletal organization. We propose that in addition to assigning cell fates, a crucial developmental function of DPP/BMP signaling is the position-specific control of epithelial architecture. 相似文献
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A polarized epithelium organized by beta- and alpha-catenin predates cadherin and metazoan origins 总被引：1，自引：0，他引：1
A fundamental characteristic of metazoans is the formation of a simple, polarized epithelium. In higher animals, the structural integrity and functional polarization of simple epithelia require a cell-cell adhesion complex that contains a classical cadherin, the Wnt-signaling protein β-catenin and the actin-binding protein α-catenin. We show that the non-metazoan Dictyostelium discoideum forms a polarized epithelium that is essential for multicellular development. Although D. discoideum lacks a cadherin homolog, we identify an α-catenin ortholog that binds a β-catenin-related protein. Both proteins are essential for formation of the epithelium, polarized protein secretion, and proper multicellular morphogenesis. Thus, the organizational principles of metazoan multicellularity may be more ancient than previously recognized, and the role of the catenins in cell polarity predates the evolution of Wnt signaling and classical cadherins. 相似文献
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为探索鹿茸的形态发生与鹿茸干细胞(包括发生干细胞和再生干细胞)内[Na~+]的关系有关,以鹿茸干细胞为模型,研究不同干性的哺乳动物干细胞内[Na~+]的差异,并鉴定引起这种差异的电压门控性钠离子通道(NaV)因素。采集并培养具有不同干性的梅花鹿鹿茸干细胞,包括生茸区骨膜细胞(AP细胞,鹿茸发生干细胞)和角柄骨膜细胞(PP细胞,鹿茸再生干细胞,其干性低于AP细胞),以鹿普通脸部骨膜细胞(FP细胞)作为对照,并采用CoroNa染色方法,通过荧光强度来分析不同类型细胞内[Na~+]的差异,结合PCR方法鉴定转录水平上NaV基因的差异,并分别用睾酮和MS-222对细胞进行处理,观测其对细胞内[Na~+]的影响。结果表明:鹿茸干细胞内[Na~+]高于FP细胞,其中AP细胞内[Na~+]高于PP细胞;NaV1.1基因在AP细胞中特异性转录;睾酮对这3种细胞内[Na~+]水平没有显著影响;但是,MS-222处理能够在一定程度上降低细胞内[Na~+]。本研究发现:鹿茸干细胞内[Na~+]与其干性一致,干性高的AP细胞内[Na~+]也相对较高;NaV1.1基因在转录水平上的差异,可能是造成AP细胞内[Na~+]高的主要原因;干扰NaV的MS-222能够在一定程度上降低细胞内[Na~+]。说明哺乳动物器官的发生和再生可能与低等动物器官上的发现类似,都与细胞内[Na~+]有关。 相似文献
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Amonlirdviman K Khare NA Tree DR Chen WS Axelrod JD Tomlin CJ 《Science (New York, N.Y.)》2005,307(5708):423-426
Planar cell polarity (PCP) signaling generates subcellular asymmetry along an axis orthogonal to the epithelial apical-basal axis. Through a poorly understood mechanism, cell clones that have mutations in some PCP signaling components, including some, but not all, alleles of the receptor frizzled, cause polarity disruptions of neighboring wild-type cells, a phenomenon referred to as domineering nonautonomy. Here, a contact-dependent signaling hypothesis, derived from experimental results, is shown by reaction-diffusion, partial differential equation modeling and simulation to fully reproduce PCP phenotypes, including domineering nonautonomy, in the Drosophila wing. The sufficiency of this model and the experimental validation of model predictions reveal how specific protein-protein interactions produce autonomy or domineering nonautonomy. 相似文献
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研究β-catenin在藏山羊牙胚发育过程中的表达与分布变化,并探讨其在牙齿发育过程中的作用机制。制备藏山羊切牙各期标本,并采用免疫组化方法观察。结果表明,帽状期在星网层、内釉上皮、牙囊均为细胞核阳性表达;钟状早期在内釉上皮、牙乳头细胞核阳性表达;钟状晚期在颈环、牙尖细胞膜阳性表达;成釉期早期在成釉质细胞、成牙本质细胞阳性表达;成釉期晚期均阴性表达。β-catenin在早期牙胚发育中有特定的时空表达模式,通过参与Wnt信号通路和作为黏附分子两种方式,对确定牙胚的形态发生重要作用。 相似文献
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在植物个体发育过程中,维管组织形态建成受多种外源及內源因子的共同影响。研究表明:植物激素、CLE
短肽信号分子、多种转录因子、热精胺、NO 等均在维管组织形态建成中发挥重要调控作用。AUX、CTK、ET、BRs、
GA 等共同参与调节原形成层与形成层细胞的增殖和分化;CLE 短肽信号分子可促进(原)形成层细胞增殖并抑制
木质部分化;HD-ZIP Ⅲ基因家族,KAN、NAC、MYB 转录因子及木质形成素与木质部、韧皮部的布局排列及发育相
关;热精胺与NO 影响着木质部细胞的分化。多种调节因子相互关联构建形成复杂的调控网络,作用于植物维管组
织的形态建成过程。 相似文献
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Notch signaling defines an evolutionarily ancient cell interaction mechanism, which plays a fundamental role in metazoan development. Signals exchanged between neighboring cells through the Notch receptor can amplify and consolidate molecular differences, which eventually dictate cell fates. Thus, Notch signals control how cells respond to intrinsic or extrinsic developmental cues that are necessary to unfold specific developmental programs. Notch activity affects the implementation of differentiation, proliferation, and apoptotic programs, providing a general developmental tool to influence organ formation and morphogenesis. 相似文献
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The steroid and thyroid hormone receptor superfamily 总被引：543，自引：0，他引：543
R M Evans 《Science (New York, N.Y.)》1988,240(4854):889-895
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Seliktar D 《Science (New York, N.Y.)》2012,336(6085):1124-1128
Hydrogels are polymeric materials distinguished by high water content and diverse physical properties. They can be engineered to resemble the extracellular environment of the body's tissues in ways that enable their use in medical implants, biosensors, and drug-delivery devices. Cell-compatible hydrogels are designed by using a strategy of coordinated control over physical properties and bioactivity to influence specific interactions with cellular systems, including spatial and temporal patterns of biochemical and biomechanical cues known to modulate cell behavior. Important new discoveries in stem cell research, cancer biology, and cellular morphogenesis have been realized with model hydrogel systems premised on these designs. Basic and clinical applications for hydrogels in cell therapy, tissue engineering, and biomedical research continue to drive design improvements using performance-based materials engineering paradigms. 相似文献
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选取编号为HL、LA08-N26、TN04-N53的3个品系杨树为材料,采用盆栽试验方法设置对照0和100mg/kg五氯酚污染胁迫处理,研究了五氯酚污染胁迫对杨树光合生理生态特征的影响。结果表明,HL和LA08-N26叶片的代谢能力和生长能力较强,可以作为植物修复五氯酚污染的树木修复材料。与对照相比,100mg/kgPCP的胁迫降低了HL的气孔导度,抑制其对弱光的利用能力和对高光强的适应性,从而抑制其光合作用;相反地,100mg/kgPCP的胁迫却促进了LA08-N26的光合作用。五氯酚胁迫对TN04-N53光合生理特征的影响不表现明显的规律。导致上述结果差异的原因较复杂,不仅与杨树品系本身的光合机构有关,还可能涉及到植物本身的基因型差异。总体而言,LA08-N26作为能在100mg/kg的PCP污染环境中具有较好光合作用潜力的品系,更具有研究价值。 相似文献
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Zhaolei WANG Kai JIANG Qinchao DING Shujun LIU Xiaobing DOU Bin DING 《农业科学与工程前沿(英文版)》2020,7(4):505-512
Penthorum chinense Pursh (PCP) is a popular traditional medicinal plant in China, widely used for the treatment of a variety of liver diseases. Although it has been long recognized that the main active elements of PCP are contained in ethyl acetate fraction (EAF), little is known so far in terms of the relative effectiveness of EAF derived from the stems versus leaves of this plant. In the current study, we prepared EAF by reflux extraction and sequential extraction from the stems (SEAF) and leaves (LEAF) of PCP and tested their hepatoprotective efficacies. The extract rates and flavonoid contents of LEAF were higher than those of SEAF. EAFs (>50 μg·mL−1) prevented lipid accumulation in cells and protected against lipotoxicity injury when the concentration exceeded 25 μg·mL−1. More than 95% free radicals released by 2,2-diphenyl-1-picrylhydrazyl (DPPH) were eliminated by 25 μg·mL−1 SEAF and 50 μg·mL−1 LEAF, respectively. Further, EAFs (25 μg·mL−1) also showed protective antioxidant effects, with the activity of LEAF being significantly higher than that of SEAF. EAFs (10 mg·mL−1) also showed similar unspecific bacteriostatic activity. In comparison with SEAF, LEAF contained more flavonoids and had a higher anti-oxidation capability and for these reasons we suggest it should be better for clinical use. 相似文献
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Phencyclidine ("PCP" or "angel dust") and some of its derivatives are psychotomimetic drugs that have been used in general anesthesia for some time. This drug blocks potassium ion channels in brain tissue, and there is a specific PCP binding to lymphocytes. In a study of the effects of this drug on immunocyte function, it was found that humoral and cellular immune responses in vitro were depressed when immunocytes were treated with PCP before biological assay. This finding has implications for PCP abuse and also for the use of its derivative in general anesthesia, where it may contribute to postoperative infection. 相似文献
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研究了薄荷的组培与快繁。适宜培养基为:诱导,MS;增殖,MS 6BA2.0mg/L NAA0.2mg/L;生根培养基为1/2MS 6BA1.0mg/L NAA0.2mg/L。首先,诱导丛生芽,然后诱导生根。将生根小苗从瓶中移于蛭石和细砂各半的基质上,最后移于培养土中。重视各环节练苗,成活率可达98%以上。笔者还叙述了薄荷的特征、特性、类型及品种与栽培技术及其广泛用途等。 相似文献
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D R Knighton T K Hunt H Scheuenstuhl B J Halliday Z Werb M J Banda 《Science (New York, N.Y.)》1983,221(4617):1283-1285
When cultured in a hypoxic environment similar to that found in the center of a wound, macrophages secreted active angiogenesis factor into the medium. Under conditions similar to those of well-oxygenated tissue, macrophages did not secrete active angiogenesis factor. Macrophages that secreted the factor at hypoxic conditions stopped secreting it when returned to room air. Thus the control of angiogenesis in wound healing may be the result of macrophages responding to tissue oxygen tension without the necessity of interacting with other cell types or biochemical signals. 相似文献