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1.
The relationship between cellular metabolism and the cell cycle machinery is by no means unidirectional. The ability of a cell to enter the cell cycle critically depends on the availability of metabolites. Conversely, the cell cycle machinery commits to regulating metabolic networks in order to support cell survival and proliferation. In this review, we will give an account of how the cell cycle machinery and metabolism are interconnected. Acquiring information on how communication takes place among metabolic signaling networks and the cell cycle controllers is crucial to increase our understanding of the deregulation thereof in disease, including cancer.  相似文献   
2.
Three-dimensional (3D) tumor spheroids are utilized in cancer research as a more accurate model of the in vivo tumor microenvironment, compared to traditional two-dimensional (2D) cell culture. The spheroid model is able to mimic the effects of cell-cell interaction, hypoxia and nutrient deprivation, and drug penetration. One characteristic of this model is the development of a necrotic core, surrounded by a ring of G1 arrested cells, with proliferating cells on the outer layers of the spheroid. Of interest in the cancer field is how different regions of the spheroid respond to drug therapies as well as genetic or environmental manipulation. We describe here the use of the fluorescence ubiquitination cell cycle indicator (FUCCI) system along with cytometry and image analysis using commercial software to characterize the cell cycle status of cells with respect to their position inside melanoma spheroids. These methods may be used to track changes in cell cycle status, gene/protein expression or cell viability in different sub-regions of tumor spheroids over time and under different conditions.  相似文献   
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4.
In this paper, the author studies the quartic bioecology differential system:Here n and q are positive constants, l、m and p are constants. The author also proves some theorems of existence and uniqueness of limit cycles of this differential system.  相似文献   
5.
ABSTRACT. Studies were completed on the natural population density of Paramecium bursaria syngen 1 and on the life cycle stages to which the individuals belonged. Green paramecia were collected from two streams once every 20 days for over one year: 413 individuals on 26 collection dates in Mikumarikyo stream and 83 individuals on 23 collection dates in Momijidani-gawa stream. Individuals in nature did not maintain at a steady density but fluctuated greatly depending on the month. It seems that conjugation occurred from April to June in the Mikumarikyo stream and from May to June in the Momijidani-gawa stream. The appearance of individuals with mating ability might be related closely to increasing population so that sexual reproduction probably occurred near the peak of the population density. The 413 individuals from Mikumarikyo stream were examined to determine their position within the life cycle; 309 (74%) were immature, 55 (13%) were adolescent, and 49 (12%) were mature. No senile individuals were observed. The fraction of individuals with mating ability was generally less than 30% at any collection. Four mating types were observed occurring with about equal frequencies in mature individuals. The results show the frequencies of the recessive genes for mating types (a and b) are higher than for dominant genes (A and B). Of 83 individuals from Momijidani-gawa stream, 44 (52%) were immature, 21 (25%) were adolescent, and 18 (21%) were mature. Again, no senile individuals were observed. Because only two mating types were found, II and III (genotypes aaB- and aabb), it seems possible that the dominant gene A was rare or absent in the Momijidani-gawa population.  相似文献   
6.
The use of natural compounds to potentiate the effect of drugs and lower their adverse effects is an active area of research. The objective is to determine the effect of combined blueberry extracts (BE) and oxaliplatin (OX) in colon cancer cells. The results demonstrated that treatments of BE/OX showed inhibitory effects on HCT-116 cell and nontoxic effect on CCD-18Co normal colon cells. Flow cytometry analysis indicated that treatment with the BE, OX or in combination could induce G0/G1 cell cycle arrest, apoptosis, increase of reactive oxygen species, and induce loss of mitochondrial membrane potential in HCT-116 cells. Furthermore, after treatments, the expression of inflammatory cytokines was decreased, cyclin D1 and CDK4 were decreased; caspases-3 and 9 were activated; the Akt/Bad/Bcl-2 pathway was modulated. Moreover, the combination treatment had a considerably higher growth inhibitory effect on human colon cancer HCT-116 cells than that of BE or oxaliplatin alone. Our results showed that BE increased the anticolon cancer effect of OX making it an attractive strategy as adjuvant therapy to potentially reduce the adverse side effects associated with chemotherapeutic drugs.  相似文献   
7.
孙明  邢勤旺  王佳晗  段妍  李楠  柴雨  董婧 《生态学报》2018,38(18):6749-6758
20世纪末以来,沙蜇在东亚水域频繁暴发,不仅影响正常的渔业生产活动,也给海洋生态系统健康带来极大危害。在室内模拟秋季降温条件,研究了不同水温(4种降温条件)与饵料量(0.42、1.25、和4.2 μg C螅状体-1d-1)对沙蜇螅状体足囊繁殖与横裂生殖的影响。结果显示:1)秋季降温速度快慢导致的积温差异对沙蜇螅状体生成足囊数有显著影响(P < 0.001),积温越大,螅状体生成的足囊数量越多,发现两者具有较好的线性关系(y=142.59x+208.39;R2=0.967),低积温条件下的足囊萌发也较少;2)饵料量对螅状体无性繁殖的影响是有一定阈值范围的,在一定饵料量范围内,螅状体生成的足囊数量随饵料量的增加而增加,而超过一定阈值范围,过剩的饵料影响水质对沙蜇螅状体反而产生负面影响。3)秋季新繁育出来的当龄沙蜇螅状体可在越冬前发生横裂生殖,但横裂生殖的螅状体比例和放碟数量均较少。试验结果说明,全球变化背景下,积温升高、饵料量小幅增加均可能导致沙蜇秋季有性繁殖的当龄螅状体在越冬前生成更多的足囊,促进诱发翌年水母暴发。  相似文献   
8.
《植物生态学报》2018,42(8):806
翅果能够依靠风力进行传播, 可能是被子植物快速散布和物种分化的一个重要因素。狭义的翅果是指果皮延伸成翅且不开裂的干果; 广义的翅果则包括果皮、花被片或苞片形成果翅的所有果实。根据果翅形态及其生长方式的不同, 广义的翅果可分为单侧翅果、周位翅果(圆翅果与蝶翅果)、棱翅果、披针翅果、翼状萼翅果、叶状苞翅果6种类型, 其空中运动方式有自旋式(单侧翅果、翼状萼翅果)、波浪式(周位翅果、叶状苞翅果)、翻滚自旋式(周位翅果)、直升机式(披针翅果、翼状萼翅果)和滚筒式(棱翅果)。棱翅果与圆翅果在被子植物基部类群樟目就有发生, 并同时出现在单子叶植物和双子叶植物中, 可能是最早出现的翅果类型。翅果的演化过程呈现出果翅数量增加、果翅偏向单侧和果翅负荷(果实质量与果翅面积之比)降低的趋势, 以利于适应较小的风并增加传播距离。果翅除了促进果实与种子的风力传播外, 还具有物理防御、调节种子萌发和促进二次传播等作用。泛热带分布的金虎尾科有着极其丰富的翅果类型, 与其多次跨洋长距离扩散密切相关, 可以作为研究翅果适应与演化的一个模式类群。结合生态和演化-发育生物学方法, 研究不同类型翅果在适应风力传播方面的差异、萼片或苞片发育成翅的分子与遗传机制、翅果不同类型的演化历史及其对被子植物物种多样性的影响等是今后值得探讨的重要问题。  相似文献   
9.
N6-methyladenosine (m6A) is the most prevalent internal mRNA modification in eukaryotes. Loss of m6A demethylase FTO increases m6A levels and inhibits adipogenesis of preadipocytes. However, its underlying mechanism remains elusive. Here, we demonstrated that silencing FTO inhibited adipogenesis of preadipocytes through impairing cell cycle progression at the early stage of adipogenesis. FTO knockdown markedly decreased the expression of CCNA2 and CDK2, crucial cell cycle regulators, leading to delayed entry of MDI-induced cells into G2 phase. Furthermore, the m6A levels of CCNA2 and CDK2 mRNA were significantly upregulated following FTO knockdown. m6A-binding protein YTHDF2 recognized and decayed methylated mRNAs of CCNA2 and CDK2, leading to decreased protein expression, thereby prolonging cell cycle progression and suppressing adipogenesis. Our work unravels that FTO regulates adipogenesis by controlling cell cycle progression in an m6A-YTHDF2 dependent manner, which provides insights into critical roles of m6A methylation in adipogenesis.  相似文献   
10.
Prospective life cycle assessment (LCA) needs to deal with the large epistemological uncertainty about the future to support more robust future environmental impact assessments of technologies. This study proposes a novel approach that systematically changes the background processes in a prospective LCA based on scenarios of an integrated assessment model (IAM), the IMAGE model. Consistent worldwide scenarios from IMAGE are evaluated in the life cycle inventory using ecoinvent v3.3. To test the approach, only the electricity sector was changed in a prospective LCA of an internal combustion engine vehicle (ICEV) and an electric vehicle (EV) using six baseline and mitigation climate scenarios until 2050. This case study shows that changes in the electricity background can be very important for the environmental impacts of EV. Also, the approach demonstrates that the relative environmental performance of EV and ICEV over time is more complex and multifaceted than previously assumed. Uncertainty due to future developments manifests in different impacts depending on the product (EV or ICEV), the impact category, and the scenario and year considered. More robust prospective LCAs can be achieved, particularly for emerging technologies, by expanding this approach to other economic sectors beyond electricity background changes and mobility applications as well as by including uncertainty and changes in foreground parameters. A more systematic and structured composition of future inventory databases driven by IAM scenarios helps to acknowledge epistemological uncertainty and to increase the temporal consistency of foreground and background systems in LCAs of emerging technologies.  相似文献   
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