细胞膜脂质流动性的不均一性与细胞分裂动力学的关系

细胞腊脂流动性在不同类属细胞存在着差异,其差异的程度取决于细胞的生理和生化特性。正常淋巴细胞、肺腺癌、肺鳞癌细胞以及结核细胞膜脂流动发生 分别为２．５１７±０．２６７、２２．５５７±３．７７１,３２．８７５±９．７０９和４．０２６±０．７２２。细胞分裂动力学与膜脂质流动性有关系。细胞分裂及其程度是膜脂质流动性差异的物质基础,同时并受细胞膜脂质的组成,脂蛋白生化以及外界因素的ｐＨ、Ｃａ＾２＋等影响,     

城郊景观动态模型研究──以沈阳市东陵区为例

基于渗透理论、马尔柯夫过程理论,采用中性模型方法,建立了3个不同的城郊景观动态模型,模型中分别介入不同自然因子和决策因子.利用模型对研究区景观进行了动态变化模拟.对模拟结果进行了评价,评价方法与指标包括:1)多分辨率拟合分析;2)最近邻概率;3)斑块大小和数目.结果发现,综合介入决策因素和自然因子的模型具有最好的效果.     

不同育秧方式和插植密度下晚籼稻群体动态结构的研究

不同育秧方式和插植密度下晚籼稻群体动态结构存在差异。旱育秧群体分蘖速度快,分蘖能力强。稀植可促进个体分蘖多发、有效穗数增多,但旱育稀植并无分蘖早发的优势。旱育稀植使主茎基部叶片变短而上部叶片变长,生育后期叶面积消长平稳,地上部干物质积累较多。旱育秧、稀植都使主茎叶总数增多,全生育期延长。     

Fusion of phosphatidylserine and mixed phosphatidylserine-phosphatidylcholine vesicles Dependence on calcium concentration and temperature

Dynamic light scattering has been used to study the temperature dependence of Ca²⁺-induced fusion of phosphatidylserine vesicles and mixed vesicles containing phosphatidylserine and different phosphatidylcholines. The final vesicle size after Ca²⁺ and EDTA incubation serves as a measure of the extent of fusion. With phosphatidylserine vesicles, the extent of fusion shows a sharp maximum at an incubation temperature which depends on the Ca²⁺ concentration between 0.8 and 2 mM. The shift in the fusion peak temperature with Ca²⁺ concentration is similar to the typical shift in the phase transition temperature with divalent cation concentration in acidic phospholipids. The results suggest a direct correlation between the fusion peak temperature and the phase transition temperature in the presence of Ca²⁺ prior to fusion. With mixed vesicles containing up to 33% of a phosphatidylcholine in at least 2 mM Ca²⁺, the extent of fusion as a function of incubation temperature also shows a maximum. The fusion peak temperature is essentially independent of the quantity and type of phosphatidylcholine and the Ca²⁺ concentration, and identical to that with pure phosphatidylserine in excess Ca²⁺. The results imply that Ca²⁺-induced molecular segregation occurs first, and fusion subsequently takes place between pure phosphatidylserine domains.     

Cytochemical evidence of an organized microtubular cytoskeleton in Xenopus laevis oocytes: involvement in the segregation of mitochondrial populations.

An organized microtubular cytoskeleton was discovered in the cytoplasm of Xenopus laevis oocytes. The microtubules were observed in 10- to 30-micron cryostat sections by indirect immunoperoxidase labeling using an antibody to tubulin. A gradual extraction of cells with a nonionic detergent was essential for good penetration of the antibody into the cells. In the cytoplasm of all previtellogenic oocytes, a dense network of criss-crossed long microtubules was associated in a basket-like structure surrounding the mitochondrial mass. At the beginning of vitellogenesis, the network meshes enlarged, while clusters of mitochondria migrated, in close association with microtubule bundles. At the beginning of vitellogenesis, the reorganization of the microtubular network, mostly in the vegetal hemisphere, occurred during the segregation of the mitochondrial populations. Reorganization is characterized by (1) a temporary enlargement of the network and close association of mitochondrial clusters with microtubular bundles, and (2) a progressive organization of a ring-shaped microtubular structure in the crown elaboration area. It is hypothesized that these modifications of the microtubular cytoskeleton contribute to the maintenance of cell shape and the polarized organization of the cell.     

Seasonal changes in the activation of crossbridge motions of isolated thick filament from Limulus striated muscle

Summary In dynamic light scattering, measurements of the intensity-intensity time correlation function from a suspension of rod-like particles of length L could reveal dynamical information related to translational and internal motions of those particles. For a suspension of thick filaments isolated from the myosin-regulated, striated muscles of Limulus at KL>1 (where K is the scattering vector), the average characteristic linewidth ( ) increased with the addition of Ca²⁺ or with the depletion of ATP. The increase in the with the addition of Ca²⁺ could be due to the presence of energy-requiring, high-frequency motions of the crossbridges activated by Ca²⁺. The increase in which occurred with the depletion of ATP was assumed to be mainly due to the thermal motions of the crossbridges after they had moved radially away from the filament backbone. The percentage increase in following the addition of Ca²⁺ was found to be seasonal, i.e., values of obtained from thick filaments isolated between the middle of June and the middle of September were smaller than those obtained during the rest of the year. The effect of temperature on the percentage increase in was also different. The increase showed a maximum at about 35°C during the summer and at about 25°C at other times. However, the percentage increase in developed under ATP-depleted conditions showed no temperature-related maximum. The number of bound Ca²⁺ per myosin molecule was 1 during the summer and 2 at other times.Abbreviations DLS dynamic light scattering - L length - K scattering vector - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis - average characteristic line width Deceased     

Cytoplasmic streaming inParamecium

Summary Certain species ofParamecium demonstrate rotational cytoplasmic streaming, in which most cytoplasmic particles and organelles flow along permanent route, in a constant direction. By means of novel methods of immobilization, observation and recording, some dynamic properties of cytoplasmic streaming have been described. It was found that the velocity profiles of coaxial layers of cytoplasm have a (parabolic) paraboidal shape and the mean output of cytoplasm flow in different examined zones of streaming is constant. As the consequence of randomly distributed elementary propulsion units within the cytoplasm, particles, which serve as markers of movement, exhibit movements of a saltatory nature; this form of movement is seen inParamecium streaming only in cases of error due to polarization of the saltating particles. Interaction of actin filaments and myosin is likely to occur under specific conditions in microcompartments of cytoplasm where local solations are generated eventually leading to contractions which might propagate on gelated neighbouring areas. Places of elementary contractions are scattered. Therefore the motile effect appears as streaming. Rotational cytoplasmic streaming inParamecium may serve as a convenient model for the study of the dynamics and function of cytoplasmic motility.     

HepG2细胞中线粒体形状的动态变化

目的:研究HepG2细胞中线粒体形状动态变化过程中的功能变化及其初步分子机制。方法:HepG2细胞经过HBSS缓冲液饥饿处理后,使用线粒体氧化磷酸化解偶联剂CCCP、脂肪酸受体GPR40/120激动剂GW9508、脂肪酸油酸OA和钙离子载体Ionomycin等4种不同药物处理,通过共聚焦显微镜观察和流式细胞分析的手段检测细胞中线粒体形状和功能发生的改变。然后,通过基因沉默Drp1,Mff或者Fis1蛋白,初步研究调控线粒体形状改变的分子机制。结果:经过CCCP和GW9508处理细胞中产生甜甜圈线粒体,而OA和Ionomycin处理产生球状线粒体。CCCP,OA和Ionomycin使线粒体去极化,CCCP、GW9508、OA或者Ionomycin单独处理在一定程度上影响细胞中活性氧化簇ROS。甜甜圈线粒体产生由Drp1介导,而球状线粒体形成依赖于Drp1和Mff。结论:线粒体的形态与其功能相互联系,Drp1和Mff蛋白对于细胞线粒体形状动态改变过程中形状的调整和适应具有很重要的作用。     

DCE-MRI联合DWI对直肠癌患者术前T、N分期及系膜淋巴结良恶性的诊断价值

摘要 目的：探讨动态对比增强磁共振(DCE-MRI)联合弥散加权成像（DWI）诊断直肠癌术前T、N分期和系膜淋巴结良恶性的价值。方法：收集2017年2月至2019年10月中国医科大学附属本溪中心医院和中国医科大学附属盛京医院接诊的80例直肠癌患者,均进行常规核磁共振成像（MRI）、DCE-MRI、DWI扫描,获得DCE-MRI、DWI定量参数[转运常数（K ^trans ）、细胞外血管外空间的体积分数（V _e ）、速率常数（K _ep ）、表观扩散系数(ADC)],比较不同T、N分期、不同性质系膜淋巴结DCE-MRI、DWI参数,及其对T、N分期和系膜淋巴结性质的诊断效能。结果：直肠癌癌灶K ^trans 、 K _ep 、V _e 高于正常肠壁,ADC低于正常肠壁（P＜0.05）。TNM分期为T_Ⅲ～Ⅳ期的患者K ^trans 、 K _ep 、V _e 高于T_Ⅰ～Ⅱ期,ADC低于T_Ⅰ～Ⅱ期（P＜0.05）;TNM分期为N₁期的患者K ^trans 、K _ep 、V _e 高于N₀期,ADC低于N₀期（P＜0.05）。联合诊断的灵敏度、特异度、阳性预测值、阴性预测值较高。结论：DCE-MRI联合DWI对直肠癌术前T、N分期、系膜淋巴结性质诊断价值较高。