Nucleoplasmic beta-actin exists in a dynamic equilibrium between low-mobility polymeric species and rapidly diffusing populations

Beta-actin, once thought to be an exclusively cytoplasmic protein, is now known to have important functions within the nucleus. Nuclear beta-actin associates with and functions in chromatin remodeling complexes, ribonucleic acid polymerase complexes, and at least some ribonucleoproteins. Proteins involved in regulating actin polymerization are also found in the interphase nucleus. We define the dynamic properties of nuclear actin molecules using fluorescence recovery after photobleaching. Our results indicate that actin and actin-containing complexes are reduced in their mobility through the nucleoplasm diffusing at approximately 0.5 microm2 s(-1). We also observed that approximately 20% of the total nuclear actin pool has properties of polymeric actin that turns over rapidly. This pool could be detected in endogenous nuclear actin by using fluorescent polymeric actin binding proteins and was sensitive to drugs that alter actin polymerization. Our results validate previous reports of polymeric forms of nuclear actin observed in fixed specimens and reveal that these polymeric forms are very dynamic.     

多种通气策略下的高浓度乙醇生产

氧气在环境胁迫强的高浓度乙醇发酵中具有重要作用.考察了自絮凝酿酒酵母在多种通气策略下的乙醇发酵及絮凝状况.使用氧化还原电位(ORP)检测发酵液中氧浓度并划分了厌氧、微氧和好氧状态.厌氧条件下的终点乙醇浓度最低(119±1.5 g/L);微氧条件下使用ORP精密控制氧气供给取得较高的乙醇浓度(131±1.8和125±1.7 g/L);在通气量0.2 vvm的好氧条件下,生物量、甘油量和乙醇损失皆最大,与最优收率相比较乙醇收率降低了12.2％.高通气量增强了细胞的絮凝能力,增大了絮凝体粒径.绘制雷达图进行综合评价,恒定通气0.05 vvm的过程在乙醇生产和絮凝各方面表现均突出.     

杉木连栽对土壤细菌群落及其抑病能力的影响

连栽导致土壤退化是制约杉木初级生产力实现的重要障碍因素,而土壤对病原菌的抑制能力决定着植物能否有效抵御病原菌侵害,是人工林土壤地力状况的重要表现。以一代、二代、三代杉木人工林和天然次生林为对象,采用平板隔空、直接对峙的方法,分析了不同代际杉木林土壤细菌群落对尖孢镰刀菌和立枯丝核菌的抑制能力。进一步利用高通量测序技术,研究了杉木林土壤细菌群落影响土壤抑病能力的生态过程。结果表明：土壤磷元素随连栽呈显著积累趋势,而土壤pH和有机质(SOM)等含量随连栽代数的增加而下降,但这些下降指标在三代杉木林与天然林土壤间无显著差异。而杉木连栽导致土壤对病原菌的抑制能力逐代降低,天然林土壤较杉木人工林对病原菌具有显著的高抑制能力。同时杉木连栽显著改变了土壤细菌群落组成,而对群落整体α-多样性影响较小,说明土壤中一些关键类群对杉木连栽响应的敏感性高于整体细菌群落的变化。进一步利用随机森林模型预测与回归分析,揭示了杉木连栽引起的土壤一些关键细菌类群丰度的降低是土壤抑病能力下降的重要原因,这些类群主要受土壤pH、SOM、TP等土壤理化因子的调控。由此,杉木长期连栽会引起土壤微环境失衡,致使土壤抑制病原菌能力下...     

青海森林生态系统中灌木层和土壤生态化学计量特征

灌木层作为森林生态系统的重要组成部分, 了解其生态化学计量特征将有助于揭示森林生态系统物质周转和养分循环等生态功能。该研究选取青海省7种主要优势林分——白桦(Betula platyphylla)林、毛白杨(Populus tomentosa)林、红桦(Betula albosinensis)林、青扦(Picea wilsonii)林、山杨(Populus davidiana)林、圆柏(Sabina chinensis)林、云杉(Picea asperata)林为研究对象, 采用野外取样和室内实验分析相结合的方法, 研究了不同林分林下灌木层不同器官(叶、枝干、根)及其表层(0-10 cm)土壤的碳(C)、氮(N)、磷(P)含量及其相关性。结果表明: 7种林分间灌木(叶、枝干、根) P含量、C:P均没有明显差异性; 山杨林、圆柏林、云杉林的林下灌木(叶、枝干、根) N含量、N:P高于白桦林、毛白杨林、红桦林和青扦林, C:N则相反。圆柏林的林下灌木生长受P限制, 其余6种林分的林下灌木生长受N限制。7种林分间土壤有机碳(SOC)和总氮(TN)含量呈现出明显差异性, 而总磷(TP)含量则差异不明显。相关性分析表明, 林下灌木(叶、枝干、根) N含量、C:N、N:P与土壤TN含量、C:N、N:P呈极显著相关性, 而P含量、C:P与土壤TP含量呈显著相关性。冗余分析表明, 林下灌木层植被C、N、P含量及生态化学计量特征受到土壤化学计量特征及各环境因子的共同影响, 其中土壤C:N、海拔、年平均气温、年降水量为主要影响因子。     

L6565小鼠白血病病毒诱发小鼠白血病

为探讨病毒与白血病发生的关系,我们用L6565小鼠白血病病毒(L6565MLV)悬液感染乳鼠,每周观察小鼠的发病情况及病理变化,并用逆转录一聚合酶链反应(RT-PCR)动态检测小鼠体内病毒核酸的分布.结果发现小鼠感染病毒后3～5周,其脾脏和淋巴结呈早期白血病的病理改变.至第10～12周小鼠发生淋巴细胞白血病,表现出耸毛、活动减少、腹膨胀等症状.病毒核酸于感染后第2周首先在小鼠胸腺、脾脏检测到,随时间延长,病毒核酸广泛分布在外周血、胸腺、脾脏、淋巴结等多种脏器组织中.本实验表明L6565小鼠白血病病毒可诱发小鼠白血病,其机制可能与病毒促使淋巴细胞向白血病细胞转化有关.     

肯塔基沙门菌的流行状况及其耐药性的研究进展

肯塔基沙门菌是引发人类和畜禽肠道疾病的重要人兽共患病原菌之一,普遍具备多重耐药性.近年来,肯塔基沙门菌在全球流行趋势逐渐上升,严重威胁畜禽健康和公共卫生安全.本文综述了国内外肯塔基沙门菌的流行状况、耐药性及防控措施研究进展,以期为肯塔基沙门菌病的防控提供参考和思路.     

The pulsed water jet for selective removal of bone cement during revision arthroplasty]

Conventional tools used in prosthetic revision surgery have a limited range of action within the narrow cement mantle. Water jet cutting technology permits tiny and precisely controlled cuts, and may therefore be an alternative method of bone cement removal. Our study compares the cutting performance on bone cement (PMMA) and bone of a pulsed water jet and a continuous water jet. The aim of the study was to establish whether selective removal of PMMA is possible. 55 bone specimens (bovine femora) and 32 specimens of PMMA were cut with a continuous and a pulsed water jet at different pressures (40 MPa, 60 MPa) and pulse frequencies (0Hz, 50Hz, 250Hz). To ensure comparability of the results, the depths of cut were related to the hydraulic power of that part of the jet actually impinging on the material. While for PMMA the power-related depth of cut increased significantly with the pulse frequency, this did not apply to bone. The cuts produced in bone were sharp-edged. Since PMMA is more brittle than bone, the water jet caused cracks that enlarged further until particles of bone broke away. Although selective removal of PMMA without doing damage to the bone was not possible at the investigated settings of the jet parameters, the results do show that a pulsed water jet can cut bone cement much more effectively than bone. This is an important advantage over conventional non-selective tools for the removal of bone cement.     

血清甘油三酯变化在急性缺血性脑卒中的临床意义

目的:探讨血清甘油三酯(TG)与急性缺血性脑卒中(AIS)早期预测之间的相关性.方法:我们收集了736例AIS患者.依据TG水平将患者分为5组.参照美国国立卫生研究院(为什么不参照我国的标准)卒中量表(NIHSS),将早期神经功能恶化(END)设定为≥4分,将新发症状开始一周后的早期临床改善(ECI)定为降低4分或以上.将各组内的END、ECI患者及两者都不是的患者进行比较.结果:高TG和低TG组患者发生END的风险显著高于正常组.高TG、低TG组以及临界组患者发生ECI的百分率显著低于正常组.多元回归分析显示高TG、低TG组以及临界组患者在END中的or值显著高于正常低值组(50-100 mg/dl).AIS患者的甘油三酯(TG)水平与预后不良呈非线性的J型相关,与良好预后呈反J形相关.结论:在AIS的早期高TG和低TG都是预后不良的危险因素.     

Selective estrogen receptor modulators protect hippocampal neurons from kainic acid excitotoxicity: differences with the effect of estradiol

Neuroprotective effects of estradiol are well characterized in animal experimental models. However, in humans, the outcome of estrogen treatment for cognitive function and neurological diseases is very controversial. Selective estrogen receptor modulators (SERMs) may represent an alternative to estrogen for the treatment or the prevention of neurodegenerative disorders. SERMs interact with the estrogen receptors and have tissue-specific effects distinct from those of estradiol, acting as estrogen agonists in some tissues and as antagonists in others. In this study we have assessed the effect of tamoxifen, raloxifene, lasofoxifene (CP-336,156), bazedoxifene (TSE-424), and 17beta-estradiol on the hippocampus of adult ovariectomized rats, after the administration of the excitotoxin kainic acid. Administration of kainic acid induced the expression of vimentin in reactive astroglia and a significant neuronal loss in the hilus. SERMs did not affect vimentin immunoreactivity in the hilus, while 17beta-estradiol significantly reduced the surface density of vimentin immunoreactive profiles. Estradiol, tamoxifen (0.4-2 mg/kg), raloxifene (0.4-2 mg/kg), and bazedoxifene (2 mg/kg) prevented neuronal loss in the hilus after the administration of kainic acid. Lasofoxifene (0.4-2 mg/kg) was not neuroprotective. These findings indicate that SERMs present different dose-dependent neuroprotective effects. Furthermore, the mechanisms of neuroprotection by SERMs and estradiol are not identical, because SERMs do not significantly affect reactive gliosis while neuroprotection by estradiol is associated with a strong down-regulation of reactive astroglia.