共查询到19条相似文献,搜索用时 93 毫秒
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基质金属蛋白酶 总被引:42,自引:0,他引:42
基质金属蛋白酶是一类分解细胞外基质组分的锌蛋白酶⒚它们在有机体生长发育中的细胞外基质逆转与重塑以及疾病中的病理损害起着极为重要的作用⒚基质金属蛋白酶的表达和活性在不同细胞水平受到严密调控,如细胞因子、生长因子以及激素的调节⒚基质金属蛋白酶以酶原形式分泌,随后被其它蛋白酶如胞浆素或非蛋白酶类化学物质如有机汞所激活⒚所有基质金属蛋白酶都受到天然抑制剂 金属蛋白酶组织抑制剂所抑制⒚两者的不平衡导致许多疾病的发生,如肿瘤侵入及转移⒚合成基质金属蛋白酶组织抑制剂所抑制,如 M arim astat 能控制肿瘤转移的发生及进一步扩散⒚本文将对基质金属蛋白酶的特征、分子区域结构、底物特性、激活机制、调控方式等方面进行最新概述⒚ 相似文献
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用电镜研究初孵扬子鳄的嗅球⒚嗅球的外颗粒层具有明、暗两种细胞⒚僧帽细胞层细胞排列紧密、规则,细胞之间无任何连接结构⒚内颗粒层见有 3~5 个细胞聚集成群,并有个别细胞出现胞质降解现象⒚除内颗粒层部分细胞外,其他各层细胞仍处于较幼稚阶段⒚胶质细胞已发生,外网状层中有薄薄的髓鞘出现⒚突触处于不同的发育阶段,大多为不对称型⒚ 相似文献
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关于假基因的研究进展 总被引:2,自引:1,他引:2
随着人类基因组计划不断深入,对于占人类基因组 97% 的非表达序列的研究也逐渐成为热点⒚在基因克隆和基因表达研究的过程中,返座假基因是我们经常碰到的问题⒚本文不仅对返座假基因的结构特征进行了小结,并且对返座假基因编码潜能、返座机理以及在进化过程中的作用进行了综述,并报道了该领域的研究成果及发展方向⒚ 相似文献
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《中国细胞生物学学报》2020,(9)
减数分裂是在有性生殖过程中高度专业化的真核细胞分裂。在减数分裂过程中,DNA复制一次,细胞连续分裂两次,子细胞染色体数目减半。在减数第一次分裂过程中为确保同源染色体正确分离,必须通过同源染色体配对、联会及重组等减数分裂特异性染色体运动。如果其中任一运动发生异常会导致先天性疾病或不孕不育症。因此,了解这些减数分裂型染色体的运动机制极为重要。该综述重点探讨了减数分裂型黏连蛋白RAD21L的特殊作用及其在哺乳动物减数分裂过程中对染色体运动的调控机制。 相似文献
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正常的卵子发生是人类成功繁育后代的关键步骤。女性胚胎发育时期,原始生殖细胞从有丝分裂转变为减数分裂,经过同源染色体配对和重组后,减数分裂被阻滞在减数第一次分裂前期的双线期。卵泡内卵母细胞的减数分裂阻滞的维持主要归因于胞质中高浓度的环磷酸腺苷。在月经周期中,卵泡刺激素和黄体生成素促进某些卵母细胞恢复减数分裂,完成排卵过程。卵母细胞减数分裂过程中发生任何缺陷都可能影响卵子发生,进而影响受精和胚胎发育过程。辅助生殖、高通量测序和分子生物学技术的快速发展,为人类认识减数分裂背后的精确分子机制以及卵母细胞成熟缺陷疾病的发病机制与诊疗提供新的思路和手段。本文主要介绍了近年来发现的调控卵子发生的生理和病理机制,涉及同源重组、减数分裂阻滞与恢复、母源mRNA降解、翻译后调节、透明带组装等过程,旨在增进相关领域研究人员对卵母细胞减数分裂的了解,并为进一步机制研究和疾病治疗提供理论基础。 相似文献
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减数分裂起始是配子发生的关键步骤。目前人们已经发现了一些减数分裂起始所必需的基因,但是对于该过程的调控基因及其作用机制还知之甚少。本实验室先前建立了精原干细胞(spermatogonial stem cells,SSCs)体外培养以及体外诱导减数分裂起始的技术体系,为更好地探究减数分裂起始调控基因及作用机理提供了良好的条件。实验室前期研究发现RNA结合蛋白RBFOX2可能调控减数分裂起始,然而RBFOX2在生殖细胞的减数分裂起始过程中的功能及作用机制还需深入研究。本研究利用慢病毒介导的转基因技术产生了RBFOX2敲降的精原干细胞系;发现RBFOX2敲降后,精原干细胞的自我更新、增殖以及分化未发生显著变化,但是减数分裂无法启动,分化型精原细胞发生明显凋亡。这一结果进一步显示了RNA结合蛋白在雄性动物减数分裂起始中的重要功能。 相似文献
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本研究建立了中国莲偶线期染色体的核型,为研究莲的减数分裂过程及分子细胞遗传学研究提供基础。 相似文献
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Ayumu Suzuki Masataka Hirasaki Akihiko Okuda 《Development, growth & differentiation》2017,59(2):61-69
Meiosis is a central event of sexual reproduction. Like somatic cells, germ cells conduct mitosis to increase their cell number, but unlike somatic cells, germ cells switch their cell division mode from mitosis to meiosis at a certain point in gametogenesis. However, the molecular basis of this switch remains elusive. In this review article, we give an overview of the onset of mammalian meiosis, including our recent finding that MYC Associated Factor X (MAX) prevents ectopic and precocious meiosis in embryonic stem cells (ESCs) and germ cells, respectively. We present a hypothetical model of a MAX‐centered molecular network that regulates meiotic entry in mammals and propose that inducible Max knockout ESCs provide an excellent platform for exploring the molecular mechanisms of meiosis initiation, while excluding other aspects of gametogenesis. 相似文献
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Asela J. Wijeratne Hong Ma 《植物学报(英文版)》2007,49(8):1199-1207
Meiosis is essential for sexual reproduction and recombination is a critical step required for normal meiosis. Understanding the underlying molecular mechanisms that regulate recombination is important for medical, agricultural and ecological reasons. Readily available molecular and cytological tools make Arabidopsis an excellent system to study meiosis. Here we review recent developments in molecular genetic analyses on meiotic recombination. These include studies on plant homologs of yeast and animal genes, as well as novel genes that were first identified in plants. The characterizations of these genes have demonstrated essential functions from the initiation of recombination by double-strand breaks to repair of such breaks, from the formation of doubie-HoUiday junctions to possible resolution of these junctions, both of which are critical for crossover formation. The recent advances have ushered a new era in plant meiosis, in which the combination of genetics, genomics, and molecular cytology can uncover important gene functions. 相似文献
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Meiosis is the crucial process by which sexually propagating eukaryotes give rise to haploid gametes from diploid cells. Several key processes, like homologous chromosomes pairing, synapsis, recombination, and segregation, sequentially take place in meiosis. Although these widely conserved events are under both genetic and epigenetic control, the accurate details of molecular mechanisms are continuing to investigate. Rice is a good model organism for exploring the molecular mechanisms of meiosis in higher plants. So far, 28 rice meiotic genes have been characterized. In this review, we give an overview of the discovery of rice meiotic genes in the last ten years, with a particular focus on their functions in meiosis. 相似文献
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Craig A Smith Kelly N Roeszler Josephine Bowles Peter Koopman Andrew H Sinclair 《BMC developmental biology》2008,8(1):85
Background
Meiosis in higher vertebrates shows a dramatic sexual dimorphism: germ cells enter meiosis and arrest at prophase I during embryogenesis in females, whereas in males they enter mitotic arrest during embryogenesis and enter meiosis only after birth. Here we report the molecular analysis of meiosis onset in the chicken model and provide evidence for conserved regulation by retinoic acid. 相似文献17.
Yu. F. Bogdanov 《Russian Journal of Genetics》2016,52(5):473-490
Inverted meiosis is observed in plants (Cyperaceae and Juncaceae) and insects (Coccoidea, Aphididae) with holocentric chromosomes, the centromeres of which occupy from 70 to 90% of the metaphase chromosome length. In the first meiotic division (meiosis I), chiasmata are formed and rodlike bivalents orient equationally, and in anaphase I, sister chromatids segregate to the poles; the diploid chromosome number is maintained. Non-sister chromatids of homologous chromosomes remain in contact during interkinesis and prophase II and segregate in anaphase II, forming haploid chromosome sets. The segregation of sister chromatids in meiosis I was demonstrated by example of three plant species that were heterozygous for chromosomal rearrangements. In these species, sister chromatids, marked with rearrangement, segregated in anaphase I. Using fluorescent antibodies, it was demonstrated that meiotic recombination enzymes Spo11 and Rad5l, typical of canonical meiosis, functioned at the meiotic prophase I of pollen mother cells of Luzula elegance and Rhynchospora pubera. Moreover, antibodies to synaptonemal complexes proteins ASY1 and ZYP1 were visualized as filamentous structures, pointing to probable formation of synaptonemal complexes. In L. elegance, chiasmata are formed by means of chromatin threads containing satellite DNA. According to the hypothesis of the author of this review, equational division of sister chromatids at meiosis I in the organisms with inverted meiosis can be explained by the absence of specific meiotic proteins (shugoshins). These proteins are able to protect cohesins of holocentric centromeres from hydrolysis by separases at meiosis I, as occurs in the organisms with monocentric chromosomes and canonical meiosis. The basic type of inverted meiosis was described in Coccoidea and Aphididae males. In their females, the variants of parthenogenesis were also observed. Until now, the methods of molecular cytogenetics were not applied for the analysis of inverted meiosis in Coccoidea and Aphididae. Evolutionary, inverted meiosis is thought to have appeared secondarily as an adaptation of the molecular mechanisms of canonical meiosis to chromosome holocentrism. 相似文献
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Watanabe Y 《Nature reviews. Molecular cell biology》2012,13(6):370-382
During mitosis, replicated chromosomes (sister chromatids) become attached at the kinetochore by spindle microtubules emanating from opposite poles and segregate equationally. In the first division of meiosis, however, sister chromatids become attached from the same pole and co-segregate, whereas homologous chromosomes connected by chiasmata segregate to opposite poles. Disorder in this specialized chromosome attachment in meiosis is the leading cause of miscarriage in humans. Recent studies have elucidated the molecular mechanisms determining chromosome orientation, and consequently segregation, in meiosis. Comparative studies of meiosis and mitosis have led to the general principle that kinetochore geometry and tension exerted by microtubules synergistically generate chromosome orientation. 相似文献