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61.
Al-Qaeda and Taliban leadership and membership appear to have been motivated, inspired, and guided by certain dreams. Their understanding of dreams seems to draw at least partly on traditional and contemporary Islamic dream theories. If this hypothesis is correct, then there is a need for the urgent study of Islamic Jihadist political/religious conversion and guidance dreams across the Middle East. The dream-as experienced, reported, and interpreted-is now a significant aspect of the global conflict between Al-Qaeda and its associates versus the core value system of Western civilization. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
62.
D. J. R. Evans Stephen Britland Peter M. Wigmore 《Development genes and evolution》1999,209(7):438-442
Fusion of mononucleated myoblasts into parallel arrays of mutinucleated myotubes is an essential step in skeletal myogenesis.
The formation of such a highly ordered structure requires myoblasts to come together, orient and align in the correct location
prior to fusion. We report here that fetal and neonatal myoblasts can use topographical features as strong guidance cues in
vitro. Myoblasts were cultured on multiple grooved substrata of varying dimensions, and the axial orientations of individual
cells were recorded. Both fetal and neonatal myoblasts aligned parallel with the direction of deep grooves (2.3–6.0 μm), which
is correlated well with the location of myoblasts in similar sized grooves during secondary myogenesis. Fetal myoblasts also
responded to shallower grooves (0.04–0.14 μm) by aligning parallel or perpendicular to the direction of the grooves, indicating
the ability of these cells to respond to fine elements normally encountered within the developing muscle architecture. In
contrast, neonatal myoblasts failed to respond to shallow grooves, adding to the suggestion that fetal and neonatal myoblasts
may represent separate populations of myoblasts. Overall, the results demonstrate that myoblasts respond to large and small
features of the physical topography in vitro and indicate that structural elements in the microenvironment of the muscle may
play a critical role in myoblast spatial organization during myogenesis.
Received: 29 May 1998 / Accepted: 17 February 1999 相似文献
63.
Sympathetic preganglionic projections of the chick are segmentally specific. Neurons from the 16th cervical (C16) and the first thoracic (T1) spinal cord segments project almost exclusively in the rostral direction, while those from the fifth thoracic (T5) to the first lumbar (L1) spinal segments project almost exclusively in the caudal direction. Neurons from the intervening spinal cord segments (T2–4) project in rostral and caudal directions. There is also a tendency for rostrally located neurons in each segment to project rostrally and caudally located neurons to project caudally. To investigate whether specific projections of preganglionic neurons are intrinsically determined by segmental origins of their cell bodies, neural tube segments were transplanted or rotated in embryos at stages 19–26; these stages include times during and after preganglionic cell birth and just prior to axon outgrowth. When the T1 neural tube segment was replaced with the T5 or T7 neural tube segment, the transplanted T5 or T7 preganglionic neurons, now in the T1 position, projected rostrally. Conversely, when the T5 or T7 neural tube segment was replaced with the T1 neural tube, the transplanted T1 preganglionic neurons projected caudally. In addition, when individual T3 spinal cord segments were rotated 180° along the A-P axis, neurons which were originally in the caudal part of the segment projected rostrally, whereas neurons originally from the rostral part of the segment projected caudally. These results show that specific projections of preganglionic neurons are not intrinsically determined by segmental origins of their cell bodies. © 1998 John Wiley & Sons, Inc. J Neurobiol 35: 371–378, 1998 相似文献
64.
目的:利用Slit排斥导向迁移和丝素蛋白,探索建立简便可行、经济实惠、作用持久的神经元导向迁移模型新方法。方法:提取SD新生鼠海马组织,以专用细胞培养片体外培养神经元,分为空白对照组、单纯丝素蛋白、单纯Slit 2N和Slit 2N与丝素蛋白混合物组(以下简称混合物组),分别随机选择不同视野下50个神经元,用显微镜拍照记录胞体坐标及突起状态,除空白对照组外,其他3组均距每个神经元100 μm处添加相应诱导物,共观察30 min,再次记录后,用免疫荧光染色法鉴定细胞性质及其阳性率。结果:单纯Slit 2N组和混合物组均可见突起向浓度低处迁移或弯曲,且长度有所缩短,空白对照组和单纯丝素蛋白组未见明显变化。突起变化的平均持续时间及平均长度差从大到小依次为混合物组、单纯Slit 2N组、单纯丝素蛋白组(P<0.05),单纯丝素蛋白组和空白对照组间无明显变化(P>0.05)。四组神经元MAP-2阳性率均达到90%以上。结论:丝素蛋白对Slit 2N诱导大鼠海马神经元迁移作用无明显影响,可有效减缓Slit 2N扩散速度,使作用时间延长,为治疗中枢神经系统疾病建立三维神经定向修复提供有利的体外实验构建基础。 相似文献
65.
The use of electric,magnetic, and electromagnetic field for directed cell migration and adhesion in regenerative medicine
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Christina L. Ross 《Biotechnology progress》2017,33(1):5-16
Directed cell migration and adhesion is essential to embryonic development, tissue formation and wound healing. For decades it has been reported that electric field (EF), magnetic field (MF) and electromagnetic field (EMF) can play important roles in determining cell differentiation, migration, adhesion, and evenwound healing. Combinations of these techniques have revealed new and exciting explanations for how cells move and adhere to surfaces; how the migration of multiple cells are coordinated and regulated; how cellsinteract with neighboring cells, and also to changes in their microenvironment. In some cells, speed and direction are voltage dependent. Data suggests that the use of EF, MF and EMF could advance techniques in regenerative medicine, tissue engineering and wound healing. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:5–16, 2017 相似文献
66.
阐明植物雄配子体与雌配子体互作的分子机理一直是植物有性生殖研究的前沿和热点。但限于研究难度较大, 很多重要科学问题仍有待回答。关于花粉管如何感知雌配子体信号从而定向生长进入胚囊以投送精细胞就是悬疑多年的问题之一。最近, 中国科学家在解析雄配子体感知雌配子体引导信号的分子机制方面取得了突破性进展。 相似文献
67.
Many external signals influence growth cone motility, pathfinding, and the formation of synapses that lead to the final map formation of the retinotectal system. Chick temporal retinal ganglion cell axons (RGCs) collapse and retract after encountering posterior tectal cells in vitro. During this process lateral extensions appear along the RGC axonal shaft. Lateral extensions appear as nascent interstitial axonal branches and also as defasciculating growth cones that are trailing along the pioneer axon. RGC branching controlled by repellent tectal cues has recently been shown to be the critical event in retinotectal map development. The intracellular mechanism underlying this phenomenon, however, is not understood. Inhibiting RhoA with either C3 toxin or inhibiting p160Rock kinase, an effector of RhoA, with Y27632 inhibited collapse, retraction, and the number of axons that showed lateral extensions. Lateral extension length increased significantly. Inhibiting Rac1A and cdc42 with cell permeable peptide inhibitors did not inhibit collapse of growth cones, but did inhibit axon retraction. In addition, the number of axons that showed lateral extensions and lateral extension length were significantly reduced. A dynamic cytoskeleton is necessary to react to incoming guidance information. This study addresses the problems of how growth cone motility and branching or defasciculation are affected by Rho‐GTPases as extracellular signals are transmitted to the cytoskeleton. © 2002 Wiley Periodicals, Inc. J Neurobiol 54: 358–369, 2003 相似文献
68.
GIT1-like proteins are GTPase-activating proteins (GAPs) for Arfs and interact with a variety of signaling molecules to function as integrators of pathways controlling cytoskeletal organization and cell motility. In this report, we describe the characterization of a Drosophila homologue of GIT1, dGIT, and show that it is required for proper muscle morphogenesis and myotube guidance in the fly embryo. The dGIT protein is concentrated at the termini of growing myotubes and localizes to muscle attachment sites in late stage embryos. dgit mutant embryos show muscle patterning defects and aberrant targeting in subsets of their muscles. dgit mutant muscles fail to localize the p21-activated kinase, dPak, to their termini. dPak and dGIT form a complex in the presence of dPIX and dpak mutant embryos show similar muscle morphogenesis and targeting phenotypes to that of dgit. We propose that dGIT and dPak are part of a complex that promotes proper muscle morphogenesis and myotube targeting during embryogenesis. 相似文献
69.
Chemosensory neurons in the olfactory epithelium (OE) project axonal processes to the olfactory bulb (OB) of the brain. During
embryonic stages, on their trajectory to the OB, the outgrowing axons traverse the so-called cribriform mesenchyme, which
is located between the OE and the OB. The molecular cues guiding these axons through the cribriform mesenchyme are largely
unknown. To identify molecules influencing the axonal trajectory in the murine cribriform mesenchyme, we performed microarray
analyses focusing on extracellular matrix (ECM) proteins present in this tissue. Thereby, the ECM protein Reelin turned out
to be an interesting candidate. Reelin was found to be expressed by numerous cells in the cribriform mesenchyme during the
embryonic stages when the first axons navigate from the OE to the OB. These cells were closely associated with olfactory axons
and apparently lack glial and neuronal markers. In the mesenchyme underlying the OE, localization of the Reelin protein was
not confined to the Reelin-expressing cells, but it was also observed to be widely distributed in the ECM—most prominently
in regions traversed by olfactory axons. Importantly, these axons were found to be endowed with the Reelin receptor very-low-density
lipoprotein receptor (VLDLR). Finally, Reelin expression was also detectable in neuronal cells of the OB, which are contacted
by VLDLR-positive olfactory axons. In summary, the results of the present study suggest that a Reelin/VLDLR signaling pathway
might contribute to the formation of olfactory projections to the OB and the establishment of initial contacts between the
incoming axons and neurons in the OB.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Funding: This work was supported by the Deutsche Forschungsgemeinschaft. 相似文献
70.
Xiaoxiang Liu Motonori Hashimoto Atsushi Yamaguchi Toshihide Yamashita 《Biochemical and biophysical research communications》2009,382(4):795-18400
Neuronal axons are guided by attractive and repulsive cues in their local environment. Since the identification of the repulsive guidance molecule (RGM) a (RGMa) as an axon repellent in the visual system, diverse functions, as part of the developing and adult central nervous system (CNS), have been ascribed to it. The binding of RGMa to its receptor neogenin has been shown to induce RhoA activation, leading to inhibitory/repulsive behavior and the collapse of the neuronal growth cone. In this paper, we provide evidence to suggest the involvement of RGMb, another member of the RGM family, in the rat CNS. RGMb inhibits neurite outgrowth in postnatal cerebellar granule neurons (CGNs) in vitro. RGMb is expressed by oligodendrocytes and neurons in the adult rat CNS, and the expression of this molecule is upregulated around the site of spinal cord injury. RGMb is present in myelin isolated from an adult rat brain. RGMb and neogenin are coexpressed in CGNs and entorhinal cortex neurons. These findings suggest that RGMb is a myelin-derived inhibitor of axon growth in the CNS. Inhibition of RGMb may provide an alternative approach for the treatment of spinal injuries. 相似文献