共查询到20条相似文献，搜索用时 31 毫秒
1.
2.
In the presence of actinomycin D (90 microg/ml), mitosis in root meristem of Allium cepa L. ceases after a delay of 36 hours. The block occurs at interphase. Differentiation of prevascular tissue is suppressed, and the evidence suggests it begins to fail before mitosis stops. Autoradiograms of roots treated with tritiated uracil show that synthesis of ribonucleic acid is blocked after mitosis fails. The effects of the antibiotic are reversible. 相似文献
3.
Hormone-dependent differentiation of mammary gland: sequence of action of hormones in relation to cell cycle 总被引：6，自引：0，他引：6
Differentiation of mouse mammary gland in vitro requires insulin, hydrocortisone, and prolactin. The epithelial cells must first divide in order to synthesize casein in response to these hormones. Insulin is required for the initiation of DNA synthesis and is also necessary during G(1) phase (after mitosis). Prolactin can elicit the overt differentiative responses after mitosis. Activity of hydrocortisone precedes that of prolactin, that is, after mitosis it is not capable of eliciting the differentiative response. 相似文献
4.
重金属胁迫下稀土调节植物细胞分裂与增殖的生理机制至今尚不完全清楚。为此,将蚕豆幼苗分别培养于营养液、6μmol.L-1氯化镉(CdCl2)以及6μmol.L-1CdCl2与2~480μmol.L-1硝酸镧[La(NO3)3]的复合溶液,14 d后检测与根尖细胞分裂和生长相关的部分生理指标。结果表明,添加2~120μmol.L-1外源La减少了根部组织对Cd的吸收,超过此剂量范围则促进了Cd的积累。同时,K、Zn、Fe等矿质元素含量,以及吲哚乙酸氧化酶同功酶及其活性呈现"U"型剂量效应的变化,而根尖细胞分裂指数和根长则呈现类似倒"U"型的剂量效应变化趋势。因此,矿质元素和吲哚乙酸氧化酶活性的失衡和干扰是La调节Cd胁迫下蚕豆幼苗根尖细胞分裂与生长的重要生理机制。 相似文献
5.
6.
Activity of the enzymes glucose-6-phosphate dehydrogenase and lactate dehydrogenase increases intermittently in synchronized cultures of Chinese hamster cells. During G(1) phase (3 hours after mitosis), midway through S phase (7 hours after mitosis) and again in late S phase (10 hours after mitosis), rapid increases in activity were observed and correlated with a net increase in cell size and total protein. The evidence suggests that this is a general phenomenon which affects a whole population of proteins and may be the expression of an endogenous cellular rhythm. 相似文献
7.
通过时苎麻多倍体及其杂交后代染色体数目、细胞有丝分裂和减数分裂行为的观察，发现具有如下特点：ａ．染色体数目呈现多样性，变幅在１２～８４之间，未发现纯合体植株；ｂ．细胞有丝分裂出现多种异常现象，如多极分裂、不均等分裂、染色体落后、核缢裂、多微核等异常行为；ｃ．减数分裂亦出现多种异常现象，包括不均等分裂、染色体落后、两极和三极分裂、出芽生殖、多微核、染色体桥等异常行为。 相似文献
8.
Differential phosphorylation of c-Abl in cell cycle determined by cdc2 kinase and phosphatase activity 总被引：19，自引：0，他引：19
The product of the c-abl proto-oncogene (c-Abl) is phosphorylated on three sites during interphase and seven additional sites during mitosis. Two interphase and all mitotic c-Abl sites are phosphorylated by cdc2 kinase isolated from either interphase or mitotic cells, with the mitotic cdc2 having an 11-fold higher activity. Inhibition of phosphatases with okadaic acid in interphase cells leads to the phosphorylation of c-Abl mitotic sites, indicating that those sites are preferentially dephosphorylated during interphase. The differential phosphorylation of c-Abl in the cell cycle is therefore determined by an equilibrium between cdc2 kinase and protein phosphatase activities. Treatment of interphase cells with okadaic acid leads to a rounded morphology similar to that observed during mitosis. 相似文献
9.
用荧光原位杂交技术检测黑麦染色质 总被引：10，自引：0，他引：10
荧光原位杂交技术（fluorescence in situ hybridization ,FISH）是一种快速、准确、直接检测和定位外源染色质的新技术。本研究荧光原位杂交用毛地黄毒苷-11-dUTP标记黑麦总DNA作探针,以检测小麦中黑麦染色质。结果如下：八倍体小黑麦（2n=8x=56）有丝分裂中期有14条染色体显示黄色,42条染色体显示红色,红色间期核显示有14个黄色亮点,表明这八倍体小黑麦含14条黑麦染色体。八倍体小黑麦中黄色黑麦染色体显C-带和H-带的末端有绿色的带。这是由于黑麦染色体末端结构异染色质含量高所致。黑麦附加系2R的间期细胞核中有1 ～ 2个黄色亮点。这表明2R含有1至2条黑麦染色体。 相似文献
10.
Inhibition of mitosis in vitro was observed in leukocytes from patients with acute infectious hepatitis. Similarly, in cultures of normal leukocytes, after the addition of small amounts of serum from patients with hepatitis, mitosis was suppressed. Althoutgh the incidence of mitosis became normal in leukocytes from convalescent patients, there were chromosomal abnormalities. 相似文献
11.
Entry into mitosis in eukaryotes requires the activity of cyclin-dependent kinase 1 (Cdk1). Cdk1 is opposed by protein phosphatases in two ways: They inhibit activation of Cdk1 by dephosphorylating the protein kinases Wee1 and Myt1 and the protein phosphatase Cdc25 (key regulators of Cdk1), and they also antagonize Cdk1's own phosphorylation of downstream targets. A particular form of protein phosphatase 2A (PP2A) containing a B55δ subunit (PP2A- B55δ) is the major protein phosphatase that acts on model CDK substrates in Xenopus egg extracts and has antimitotic activity. The activity of PP2A-B55δ is high in interphase and low in mitosis, exactly opposite that of Cdk1. We report that inhibition of PP2A-B55δ results from a small protein, known as α-endosulfine (Ensa), that is phosphorylated in mitosis by the protein kinase Greatwall (Gwl). This converts Ensa into a potent and specific inhibitor of PP2A-B55δ. This pathway represents a previously unknown element in the control of mitosis. 相似文献
12.
Asymmetric segregation of P granules during the first four divisions of the Caenorhabditis elegans embryo is a classic example of cytoplasmic partitioning of germline determinants. It is thought that asymmetric partitioning of P granule components during mitosis is essential to distinguish germline from soma. We have identified a mutant (pptr-1) in which P granules become unstable during mitosis and P granule proteins and RNAs are distributed equally to somatic and germline blastomeres. Despite symmetric partitioning of P granule components, pptr-1 mutants segregate a germline that uniquely expresses P granules during postembryonic development. pptr-1 mutants are fertile, except at high temperatures. Hence, asymmetric partitioning of maternal P granules is not essential to specify germ cell fate. Instead, it may serve to protect the nascent germline from stress. 相似文献
13.
Tsai MY Wang S Heidinger JM Shumaker DK Adam SA Goldman RD Zheng Y 《Science (New York, N.Y.)》2006,311(5769):1887-1893
Mitotic spindle morphogenesis is a series of highly coordinated movements that lead to chromosome segregation and cytokinesis. We report that the intermediate filament protein lamin B, a component of the interphase nuclear lamina, functions in spindle assembly. Lamin B assembled into a matrix-like network in mitosis through a process that depended on the presence of the guanosine triphosphate-bound form of the small guanosine triphosphatase Ran. Depletion of lamin B resulted in defects in spindle assembly. Dominant negative mutant lamin B proteins that disrupt lamin B assembly in interphase nuclei also disrupted spindle assembly in mitosis. Furthermore, lamin B was essential for the formation of the mitotic matrix that tethers a number of spindle assembly factors. We propose that lamin B is a structural component of the long-sought-after spindle matrix that promotes microtubule assembly and organization in mitosis. 相似文献
14.
Torres-Rosell J De Piccoli G Cordon-Preciado V Farmer S Jarmuz A Machin F Pasero P Lisby M Haber JE Aragón L 《Science (New York, N.Y.)》2007,315(5817):1411-1415
Cellular checkpoints prevent mitosis in the presence of stalled replication forks. Whether checkpoints also ensure the completion of DNA replication before mitosis is unknown. Here, we show that in yeast smc5-smc6 mutants, which are related to cohesin and condensin, replication is delayed, most significantly at natural replication-impeding loci like the ribosomal DNA gene cluster. In the absence of Smc5-Smc6, chromosome nondisjunction occurs as a consequence of mitotic entry with unfinished replication despite intact checkpoint responses. Eliminating processes that obstruct replication fork progression restores the temporal uncoupling between replication and segregation in smc5-smc6 mutants. We propose that the completion of replication is not under the surveillance of known checkpoints. 相似文献
15.
Checkpoints: controls that ensure the order of cell cycle events 总被引：282，自引：0，他引：282
The events of the cell cycle of most organisms are ordered into dependent pathways in which the initiation of late events is dependent on the completion of early events. In eukaryotes, for example, mitosis is dependent on the completion of DNA synthesis. Some dependencies can be relieved by mutation (mitosis may then occur before completion of DNA synthesis), suggesting that the dependency is due to a control mechanism and not an intrinsic feature of the events themselves. Control mechanisms enforcing dependency in the cell cycle are here called checkpoints. Elimination of checkpoints may result in cell death, infidelity in the distribution of chromosomes or other organelles, or increased susceptibility to environmental perturbations such as DNA damaging agents. It appears that some checkpoints are eliminated during the early embryonic development of some organisms; this fact may pose special problems for the fidelity of embryonic cell division. 相似文献
16.
The extract of soluble proteins from Lilium anthers is characterized by four electrophoretic components. Three of the components show quantitative differences markedly correlated with the synchronized division of the microspores contained within the anthers. One of the components increases in amount before mitosis and disappears at mitosis; two of the components have peak values at the time of mitosis and decrease thereafter; a fourth component remains relatively constant in amount throughout. 相似文献
17.
多裂蒲公英(T.dissectu Ledeb)染色体的核型分析 总被引：2，自引：0，他引：2
利用根尖压片法对多裂蒲公英进行有丝分裂观察及核型分析,统计观察了50个准确计数染色体的根尖有丝分裂中期细胞。实验结果表明:多裂蒲公英的染色体数为2n=32,其核型公式为2n=32=28m+2sm+2T。利用有丝分裂过程当中的染色体核型,可以明确区分蒲公英属植物在表现型上难以区别的类型,染色体的数目、相对长度、着丝粒位置和随体有无等都可以作为蒲公英属植物的分类指标而被利用。 相似文献
18.
Nuclear reassembly excludes large macromolecules 总被引：6，自引：0，他引：6
Interphase nucleus and cytoplasm are distinct compartments, whose soluble macromolecular contents mix when the nuclear envelope disassembles at mitosis. To determine how their interphase identities are reestablished, fibroblasts were loaded with fluorescent dextrans and then allowed to divide. Large dextrans (molecular weight of 40,000 or more) were excluded from condensed mitotic chromosomes and from newly formed, postmitotic interphase nuclei. Therefore, postmitotic reassembly of the nucleus as a compartment distinct from cytoplasm occurs by exclusion not only of organelles but also of soluble macromolecules. This might occur by exclusion of macromolecules from condensed chromatin throughout mitosis and completion of nuclear envelope assembly before nuclear expansion. 相似文献
19.
紫杉醇抗肿瘤机理与毒副作用 总被引：5，自引：0，他引：5
文章综合叙述了紫杉醇的抗肿瘤机理和它的毒副作用。紫杉醇的抗癌机理主要是通过抑制微管解聚使肿瘤细胞有丝分裂终止促进肿瘤细胞凋亡,最后导致肿瘤细胞死亡;紫杉醇体内免疫调节功能也可以对肿瘤细胞起杀伤或抑制作用。另外,对紫杉醇的一般毒性、生殖毒性、遗传毒性进行了介绍。 相似文献
20.
吴国江 《新疆农业大学学报》1988,(4)
本实验观察的西瓜作物新品种之一,“金夏”的核型为:2n=2x=20m+25m。染色体长度范围在1.98μ—3.31μ之间,除第二对染色体为次中部着丝点染色体外,其余的染色体都具中部着丝点染色体,西瓜作物的细胞制片的材料预处理过程以0.05—0.1％的秋水仙素在0—4℃的低温下处理10—12小时为最佳。 相似文献