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31.
基因治疗是未来临床医学最具潜力的治疗方式,目前阻碍临床基因治疗发展的主要因素是缺乏安全和高效的基因载体,因此研究理想的非病毒转基因载体具有重要的意义.构建了由质粒DNA(D)-抗DNA抗体(A)-阳离子脂质体(C)组成的三元复合纳米基因载体(DAC),研究表明,三组分在磷酸缓冲液中可通过分子组装形成复合纳米胶束,DAC在细胞培养中表现出显著高效的基因表达,DAC在血管平滑肌细胞中的基因转染效率比不含抗DNA抗体的二元组合(DC)高4倍,比不含阳离子脂质体的二元组合(DA)约高11倍.激光共聚焦荧光显微观察证明,DAC细胞摄取量和DNA进入细胞核的量均明显高于对照组,而DC二元组合(不含抗DNA抗体)的DNA很少进入细胞核,细胞在DAC存在下生长正常.未发现细胞毒性.研究结果提示,DAC的作用机理主要是三元复合胶束中DNA的装载量比二元载体大得多,抗DNA抗体与阳离子脂质体的协同作用明显有利于DNA被细胞摄取和胞吞,从而提高了基因的转染和表达. 相似文献
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Sequence variations in small-subunit ribosomal RNAs of Hartmannella vermiformis and their phylogenetic implications 总被引:1,自引:0,他引:1
Evidence of associations between free-living amoebas and human disease has
been increasing in recent years. Knowledge about phylogenetic relationships
that may be important for the understanding of pathogenicity in the genera
involved is very limited at present. Consequently, we have begun to study
these relationships and report here on the phylogeny of Hartmannella
vermiformis, a free-living amoeba that can harbor the etiologic agent of
Legionnaires' disease. Our analysis is based on studies of small-subunit
ribosomal RNA genes (srDNA). Nucleotide sequences were determined for
nuclear srDNA from three strains of H. vermiformis isolated from the United
Kingdom, Germany, and the United States. These sequences then were compared
with a sequence previously obtained for a North American isolate by J. H.
Gunderson and M. L. Sogin. The four genes are 1,840 bp long, with an
average GC content of 49.6%. Sequence differences among the strains range
are 0.38%-0.76%. Variation occurs at 19 positions and includes 2
single-base indels plus 14 monotypic and 3 ditypic single-base
substitutions. Variation is limited to eight helix/loop structures
according to a current model for srRNA secondary structure. Parsimony,
distance, and bootstrap analyses used to examine phylogenetic relationships
between the srDNA sequences of H. vermiformis and other eukaryotes
indicated that Hartmannella sequences were most closely related to those of
Acanthamoeba and the alga Cryptomonas. All ditypic sites were consistent
with a separation between European and North American strains of
Hartmannella, but results of other tests of this relationship were
statistically inconclusive.
相似文献
34.
Cell-to-cell transfer of glial proteins to the squid giant axon: The glia- neuron protein transfer hypothesis 下载免费PDF全文
The hypothesis that glial cells synthesize proteins which are transferred to adjacent neurons was evaluated in the giant fiber of the squid (Loligo pealei). When giant fibers are separated from their neuron cell bodies and incubated in the presence of radioactive amino acids, labeled proteins appear in the glial cells and axoplasm. Labeled axonal proteins were detected by three methods: extrusion of the axoplasm from the giant fiber, autoradiography, and perfusion of the giant fiber. This protein synthesis is completely inhibited by puromycin but is not affected by chloramphenicol. The following evidence indicates that the labeled axonal proteins are not synthesized within the axon itself. (a) The axon does not contain a significant amount of ribosomes or ribosomal RNA. (b) Isolated axoplasm did not incorporate [(3)H]leucine into proteins. (c) Injection of Rnase into the giant axon did not reduce the appearance of newly synthesized proteins in the axoplasm of the giant fiber. These findings, coupled with other evidence, have led us to conclude that the adaxonal glial cells synthesize a class of proteins which are transferred to the giant axon. Analysis of the kinetics of this phenomenon indicates that some proteins are transferred to the axon within minutes of their synthesis in the glial cells. One or more of the steps in the transfer process appear to involve Ca++, since replacement of extracellular Ca++ by either Mg++ or Co++ significantly reduces the appearance of labeled proteins in the axon. A substantial fraction of newly synthesized glial proteins, possibly as much as 40 percent, are transferred to the giant axon. These proteins are heterogeneous and range in size from 12,000 to greater than 200,000 daltons. Comparisons of the amount of amino acid incorporation in glia cells and neuron cell bodies raise the possibility that the adaxonal glial cells may provide an important source of axonal proteins which is supplemental to that provided by axonal transport from the cell body. These findings are discussed with reference to a possible trophic effect of glia on neurons and metabolic cooperation between adaxonal glia and the axon. 相似文献
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Bethany L. Suderman Bala Krishnamoorthy 《Computer methods in biomechanics and biomedical engineering》2013,16(7):735-744
In this paper, we studied the effects of wrapping surfaces on muscle paths and moment arms of the neck muscle, semispinalis capitis. Sensitivities to wrapping surface size and the kinematic linkage to vertebral segments were evaluated. Kinematic linkage, but not radius, significantly affected the accuracy of model muscle paths compared to centroid paths from images. Both radius and linkage affected the moment arm significantly. Wrapping surfaces that provided the best match to centroid paths over a range of postures had consistent moment arms. For some wrapping surfaces with poor matches to the centroid path, a kinematic method (tendon excursion) predicted flexion moment arms in certain postures, whereas geometric method (distance to instant centre) predicted extension. This occurred because the muscle lengthened as it wrapped around the surface. This study highlights the sensitivity of moment arms to wrapping surface parameters and the importance of including multiple postures when evaluating muscle paths and moment arm. 相似文献
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Pauline?AaltenEmail author Inez?HGB?Ramakers Geert?Jan?Biessels Peter?Paul?de Deyn Huiberdina?L?Koek Marcel?GM?OldeRikkert Ania?M?Oleksik Edo?Richard Lieke?L?Smits John?C?van Swieten Laura?K?Teune Aad?van der Lugt Frederik?Barkhof Charlotte?E?Teunissen Nico?Rozendaal Frans?RJ?Verhey Wiesje?M?van der Flier 《BMC neurology》2014,14(1):254
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