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81.
82.
Dystrophin is a plasma membrane-associated cytoskeletal protein of the spectrin superfamily. The dystrophin cytoskeleton has been first characterized in muscle. Muscular 427 kDa dystrophin binds to subplasmalemmal actin filaments via its amino-terminal domain. The carboxy-terminus of dystrophin binds to a plasma membrane anchor, beta-dystroglycan, which is associated on the external side with the extracellular matrix receptor, alpha-dystroglycan, that binds to the basal lamina proteins laminin-1, laminin-2, and agrin. In the muscle, the dystroglycan complex is associated with the sarcoglycan complex that consists of several glycosylated, integral membrane proteins. The absence or functional deficiency of the dystrophin cytoskeleton is the cause of several types of muscular dystrophies including the lethal Duchenne muscular dystrophy (DMD), one of the most severe and most common genetic disorders of man. The dystrophin complex is believed to stabilize the plasma membrane during cycles of contraction and relaxation. Muscular dystrophin and several types of dystrophin variants are also present in extramuscular tissues, e.g. in distinct regions of the central nervous systems including the retina. Absence of dystrophin from these sites is believed to be responsible for some extramuscular symptoms of DMD, e.g. mental retardation and disturbances in retinal electrophysiology (reduced b-wave in electroretinograms). The reduced b-wave in electroretinograms indicated a disturbance of neurotransmission between photoreceptors and ON-bipolar cells. At least two different dystrophin variants are present in photoreceptor synaptic complexes. One of these dystrophins (Dp260) is virtually exclusively expressed in the retina. In the neuroretina, dystrophin is found in significant amounts in the invaginated photoreceptor synaptic complexes. At this location dystrophin colocalizes with dystroglycan. Agrin, an extracellular ligand of alpha-dystroglycan, is also present at this location whereas the proteins of the sarcoglycan complex appear to be absent in photoreceptor synaptic complexes. Dystrophin and dystroglycan are located distal from the ribbon-containing active synaptic zones where both proteins are restricted to the photoreceptor plasma membrane bordering on the lateral sides of the synaptic invagination. In addition, some neuronal profiles of the postsynaptic complex also contain dystrophin and beta-dystroglycan. These profiles appear to belong at least in part to projections of the photoreceptor terminals into the postsynaptic dendritic complex. In view of the abnormal neurotransmission between photoreceptors and ON-bipolar cells in DMD patients the dystrophin/beta-dystroglycan-containing projections of photoreceptor presynaptic terminals into the postsynaptic dendritic plexus might somehow modify the ON-bipolar pathway. Another retinal site associated with dystrophin/beta-dystropglycan is the plasma membrane of Müller cells where dystrophin/beta-dystroglycan appear to be present at particular high concentrations. At this location the dystrophin/dystroglycan complex may play a role in the attachment of the retina to the vitreous, and, under pathological conditions, in traction-induced retinal detachment. 相似文献
83.
本文介绍了可在微机上实现大规模电信网践模拟的实用化软件SIMUNET,及基所采用的无时钟事件追踪法。该软件可用规划中的电信网络和实际网路的模拟及性能评价,也可用于不同流量控制算法的评价。文中给出一个评价实例。 相似文献
84.
雾化水流计算模式 总被引:21,自引:1,他引:20
梁在潮 《水动力学研究与进展(A辑)》1992,7(3):247-255
本文描述了雾化水流现象并提出了雾化水流的一个计算模型。得出了雾化水流影响领域的各种不同的计算公式和方法。 相似文献
85.
Chung S.S. Shui-Ming Cheng Lee R.G.-H. Song-Nian Kuo Mong-Song Liang 《Electron Devices, IEEE Transactions on》1997,44(12):2220-2226
This paper reports a simple I-V method for the first time to determine the lateral lightly-doped source/drain (S/D) profiles (n- region) of LDD n-MOSFETs. One interesting result is the direct observation of the reverse-short-channel effect (RSCE). It is observed that S/D n- doping profile is channel length dependent if reverse short-channel effect exists as a result of the interstitial imperfections caused by Oxide Enhanced Diffusion (OED) or S/D implant. Not only the lateral profiles for long-channel devices but also for short-channel devices can be determined. One other practical application of the present method for device drain engineering has been demonstrated with a LATID MOS device drain engineering work. It is convincible that the proposed method is well suited for the characterization and optimization of submicron and deep-submicron MOSFETs in the current ULSI technology 相似文献
86.
87.
本文根据ITU-T最新的Q.2971协议,以及笔者所从事的实际课题,提出一整套B-ISDN第三层UNI信令的软件实现策略,其特点是能同时满足用户对点到点以及点到多点广播这两种通信方式的要求,而且可以动态配置。 相似文献
88.
焦化防砂室内实验研究 总被引:2,自引:1,他引:1
油井防砂工艺技术的研究与发展对疏松砂岩油藏的正常开采至关重要.焦化防砂是通过向地层内注入热空气使原油在高温下发生氧化裂解生成焦炭从而将地层砂固结的一种防砂新技术.为了对该项技术进行全面系统的理论分析与评价,设计并制作了一套焦化防砂实验装置,利用该装置进行了焦化防砂室内实验研究.焦化效果以岩样的抗压强度进行评价,实验结果表明,影响焦化后岩样抗压强度的主要因素为空气最高温度、处理时间和空气流量.此外,对焦化处理后的岩样所作的岩样组成分析揭示出,稠油胶结机理为氧化作用使部分油分和胶质变成沥青质,沥青质受到高度的缩合作用而成为高分子量的甲苯不溶物.由于新生胶质的氧化比原生胶质的氧化困难得多,因此适合焦化防砂的油层,其原油必须含有一定量的原生胶质和沥青质. 相似文献
89.
Recent studies have suggested that cytokines play a critical role in the pathophysiology of alopecia areata; however, no information is available regarding the difference in cytokine profiles in these patients. Serum levels of cytokines, including interferon gamma (IFN-gamma), tumor necrosis factor alpha, interleukin 1 alpha (IL-1 alpha), IL-2, IL-4, and IL-6, were measured using radioimmunoassay or enzyme-linked immunosorbent assay techniques in patients with the localized form and the extensive form (alopecia universalis). The serum levels of IL-1 alpha and IL-4 were significantly elevated in patients with the localized form. In contrast, the serum levels of IFN-gamma and IL-2 were significantly elevated in patients with the extensive form. These results indicate that immune responses in the localized form and the extensive form of alopecia areata are regulated by Th2 cytokines and Th1 cytokines, respectively. 相似文献
90.
An elastic half plane with an oblique edge crack is considered in this paper. A pair of concentrated forces or point dislocations is assumed to act at an arbitrary point in the half plane. The half plane with an edge crack is first mapped into a unit circle by a rational mapping function so that the following analysis can be carried out on the mapped plane analytically. Then the complex stress functions are derived by separating the whole problem into two parts; one is the principal part corresponding to the infinite plane acted on by concentrated forces or dislocations, the other is the holomorphic part, which can be determined by making use of the property of regularity of complex stress functions. The stress intensity factors of the crack can be calculated with different inclined angles of the crack, and the displacement and stress components at an arbitrary position in the half plane can be expressed explicitly. 相似文献