Helical structures of ESCRT-III are disassembled by VPS4

During intracellular membrane trafficking and remodeling, protein complexes known as the ESCRTs (endosomal sorting complexes required for transport) interact with membranes and are required for budding processes directed away from the cytosol, including the budding of intralumenal vesicles to form multivesicular bodies; for the budding of some enveloped viruses; and for daughter cell scission in cytokinesis. We found that the ESCRT-III proteins CHMP2A and CHMP3 (charged multivesicular body proteins 2A and 3) could assemble in vitro into helical tubular structures that expose their membrane interaction sites on the outside of the tubule, whereas the AAA-type adenosine triphosphatase VPS4 could bind on the inside of the tubule and disassemble the tubes upon adenosine triphosphate hydrolysis. CHMP2A and CHMP3 copolymerized in solution, and their membrane targeting was cooperatively enhanced on planar lipid bilayers. Such helical CHMP structures could thus assemble within the neck of an inwardly budding vesicle, catalyzing late steps in budding under the control of VPS4.     

Single cell layered heart: electromechanical properties of the heart of Boltenia ovifera

The heart of Boltenia ovifera (the sea potato) is a tubular structure formed by a single layer of myocardial cells. Electron microscopic studies show that each cell contains a single myofibril located adjacent to the luminal surface of the cell. Electrical and mechanical measurement of a cannulated perfused heart demonstrate that only the luminal membrane is excitabble and elicits contraction on depolarization. Calcium and magnesium exert antagonistic effects on tension, and potassium depolarizes the myocardium and produces contractures when the luminal membrane is exposed to various concentrations of these ions. The extraluminl membrane does not respond electrically or mechanically to calcium magnesium or potassium, and its potential seems to be effectively "clamped" by the luminal membrane. Functionaly, therefore, this heart consists of a single active membrane with the adjacent contractile apparatus.     

Wnt5a control of cell polarity and directional movement by polarized redistribution of adhesion receptors

Mechanisms by which Wnt pathways integrate the organization of receptors, organelles, and cytoskeletal proteins to confer cell polarity and directional cell movement are incompletely understood. We show that acute responses to Wnt5a involve recruitment of actin, myosin IIB, Frizzled 3, and melanoma cell adhesion molecule into an intracellular structure in a melanoma cell line. In the presence of a chemokine gradient, this Wnt-mediated receptor-actin-myosin polarity (W-RAMP) structure accumulates asymmetrically at the cell periphery, where it triggers membrane contractility and nuclear movement in the direction of membrane retraction. The process requires endosome trafficking, is associated with multivesicular bodies, and is regulated by Wnt5a through the small guanosine triphosphatases Rab4 and RhoB. Thus, cell-autonomous mechanisms allow Wnt5a to control cell orientation, polarity, and directional movement in response to positional cues from chemokine gradients.     

Intracellular calcium: its movement during pentylenetetrazole-induced bursting activity

The intracellular calcium concentration in the cytoplasm decreased and the calcium concentration near the cell membrane increased during bursting activity induced by pentylenetetrazole in snail neuron. Incubation in medium containing cobalt chloride or lanthanum chloride did not change this tendency, which suggests that this calcium distribution change is due to the stored calcium in the subcellular structure moving toward the cell membrane.     

白藜芦醇对HA-VSMC细胞膜电位和钙离子的影响

[目的]研究白藜芦醇对人主动脉血管平滑肌细胞(T/G HA-VSMC)膜电位和游离钙浓度的影响。[方法]用荧光染料DiBAC4(3)和Fluo-3-AM分别标记细胞,在流式细胞仪上分别测定细胞膜电位及胞内游离钙浓度的变化。[结果]给予Res后,HA-VSMC膜电位去极化,胞内游离钙浓度升高。[结论]Res可去极化HA-VSMC细胞膜电位,促进钙内流。     

Divalent cations directly affect the conductance of excised patches of rod photoreceptor membrane

Phototransduction in rod cells is likely to involve an intracellular messenger system that links the absorption of light by rhodopsin to a change in membrane conductance. The direct effect of guanosine 3',5'-monophosphate (cGMP) on excised patches of rod outer segment membrane strongly supports a role for cGMP as an intracellular messenger in phototransduction. It is reported here that magnesium and calcium directly affect the conductance of excised patches of rod membrane in the absence of cGMP and that magnesium, applied to intact rod cells, blocks a component of the cellular light response. The divalent cation-suppressed conductance in excised patches showed outward rectification and cation-selective permeability resembling those of the light-suppressed conductance measured from the intact rod cell. The divalent cation-suppressed conductance was partly blocked by a concentration of the pharmacological agent L-cis-diltiazem that blocked all of the cGMP-activated conductance. Divalent cations may act, together with cGMP, as an intracellular messenger system that mediates the light response of the rod photoreceptor cell.     

2月龄绿孔雀消化系统组织学观察

2月龄绿孔雀的消化器官各段肌层发达,消化腺发达。食管粘膜为复层扁平上皮,浅层细胞未出现角质化。食管腺由单层枉状上皮构成,开口处为复层扁平上皮,粘膜肌异常明显。嗉囊的粘膜上皮和腺体与食管相似,粘膜下层不明显。腺胃有浅层单管腺和深层复管腺,浅层单管腺由单层柱状上皮构成。小肠绒毛上皮是单层柱状上皮,粘膜肌不明显,有中央乳糜管,无十二指肠腺。十二指肠后段,固有层有淋巴孤结。空肠、回肠固有层有淋巴孤结。盲肠的固有层有淋巴孤结和丰富的肠腺,肌层发达。肝小叶间界限不清,血窦中可见大量扁平的内皮细胞和多突的星状细胞。胰脏的小叶界限不清,内分泌部有丰富的毛细血管。     

酸性电解水对肉源性荧光假单胞菌的致死效应

【目的】研究酸性电解水（AEW）能否有效控制肉源性荧光假单胞菌,探究处理后菌体变化,为新型杀菌剂的开发提供思路。【方法】使用不同有效氯浓度酸性电解水（20、40和60 mg?L ^-1）将肉源性荧光假单胞菌分别处理5、10、15、20、25和30 min后,通过平板计数检测酸性电解水对肉源性荧光假单胞菌的致死效果;收集未处理及20、40和60 mg?L ^-1酸性电解水各处理5 min后菌液,利用扫描电子显微镜观测酸性电解水对肉源性荧光假单胞菌细胞形态的影响;利用多种荧光探针检测酸性电解水对肉源性荧光假单胞菌细胞膜完整性、胞内pH、胞内ATP浓度、膜电位的影响;提取胞外聚合物（EPS）探究酸性电解水与EPS的相互作用。 【结果】20、40和60 mg?L ^-1的酸性电解水均可在5 min内杀死10 ⁷CFU/mL肉源性荧光假单胞菌,酸性电解水浓度大于40 mg·L ^-1时对肉源性荧光假单胞菌的杀菌效果没有显著影响（P>0.05）,10 min处理后均已无活菌检出。扫描电子显微镜结果表明3种浓度酸性电解水的处理均可使肉源性荧光假单胞菌菌体干瘪皱缩,失去原本饱满的细胞形态,60 mg·L ^-1电解水处理下破损程度最大。酸性电解水可显著降低肉源性荧光假单胞菌的膜完整性、胞内pH、膜电位、胞内ATP浓度和EPS含量（P<0.05）。20、40和60 mg·L ^-1酸性电解水处理后菌体膜完整性分别降低到2.26%、1.87%和1.20%,膜电位分别消散40%、50%和50%,胞内pH由7.50分别降低到6.53、5.90和5.83,3种浓度处理后胞内ATP浓度已降至最低。杀菌效果显著依赖于酸性电解水浓度的升高,当处理浓度高于40 mg?L ^-1时,胞内pH、膜电位和胞内ATP浓度的降低无显著差异。酸性电解水处理下EPS中蛋白、总糖含量显著降低,松散胞外聚合物 （L-EPS）中蛋白和总糖分别降低71.08%和62.23%,而紧密胞外聚合物（B-EPS）中蛋白和总糖分别降低99.32%和40.62%。当EPS反向添加到酸性电解水中时则可显著降低酸性电解水氧化还原电位（ORP）（P<0.05）,但对有效氯浓度（ACC）和pH没有显著影响（P>0.05）。 【结论】酸性电解水对肉源性荧光假单胞菌具有良好的杀菌效果,可破坏肉源性荧光假单胞菌细胞膜,同时EPS对酸性电解水杀菌效果具有一定的阻碍作用。     

Effect of Hypoxia on Ca^2＋ Concentration in Broiler＇s Cardiac Muscle Cells

The purpose of this research was to study the effect of hypoxia on the Ca^2＋ concentration in broiler＇s cardiac muscle cells （CMCs）. The concentration of Ca^2＋ in the CMC was observed using a laser scanning confocal microscope （LSCM）. The results showed that hypoxia could significantly increase intracellular Ca^2＋（normal oxygen, 99.3 ＋_ 13.1; hypoxia, 129.4 ＋_ 24.3, P 〈 0.01） in CMCs. The Ca^2＋ antagonist （nifedipine, verapamil） could significantly restrain the Ca^2＋ influx across the cell membrane of CMC treated by hypoxia （CMC： hypoxia ＋ verapamil, 100.9± 28.2; hypoxia ＋ nifedipine, 107.6± 27.7; P 〈 0.01）. The results showed hypoxia could increase intracellular Ca^2＋ concentration of CMC, and the Ca^2＋ antagonist could restrain the Ca^2＋ influx across the cell membrane of CMC treated by hypoxia.     

Membrane alterations in hemolysis: Internalization of plasmalemma induced by primaquine

Incubation of normal human erythrocytes with primaquine, a derivative of 8-aminoquinoline, results in internalization of the cell membrane and the formation of intracellular vacuoles. These changes are similar to those observed in other types of cells in pinocytosis. The reduction in surface cell membrane which accompanies internalization of plasmalemma may be generally significant in the destruction of red cells.     

柞蚕杀菌肽对桉树青枯病假单胞菌的杀菌作用

桉树、木麻黄青枯病是广东省林业主要病害、近年为害猖獗导致严重损失。本文报道柞蚕杀菌肽Ｄ对桉树、木麻黄青枯病假单胞菌的杀菌作用。以荧光黄染料隅联的杀菌肽作用于青枯病假单胞菌，用电镜及激光共焦扫描显微镜观察，发现杀菌肽能迅速地将菌体包围，作用于细胞膜，造成许多小孔并进入胞内，尔后损伤的小孔扩大形成喇叭口，内含物由此泄出胞外，最后菌体变成空囊而死亡。     

似锥低颈吸虫和宫川棘口吸虫的排泄系统超微结构观察（复殖目：棘口科）

本文运用透射电镜对棘口科似锥低颈吸虫（Ｈｙｐｏｄｅｒａｅｕｍｃｏｎｏｉｄｅｕｍ）和宫川棘口吸虫（Ｅｃｈｉｎｏａｓｏｔｏｍａｍｉｙａｇａｗａｉ）的排泄系统进行了初步研究和比较。结果显示，两种吸虫的排泄系统均由焰细胞、排泄管和排泄囊组成。似锥低颈吸虫焰细胞的纤毛数为１１５条，宫川棘口吸虫为１２５条。似锥低颈吸虫的排泄管和排泄囊壁内面具有丰富的微绒毛，而宫川棘口吸虫则含少许微绒毛。两种吸虫的排泄管壁合胞体和管腔内含有丰富的脂滴。两种吸虫排泄系统均具有吞噬作用。     

Depolarization of alfalfa root hair membrane potential by Rhizobium meliloti Nod factors

Although much is known about the bacterial genetics of early nodulation, little is known about the plant cell response. Alfalfa root hair cells were impaled with intracellular microelectrodes to measure a membrane potential depolarizing activity in Rhizobium meliloti cell-free filtrates, a plant response dependent on the bacterial nodulation genes. The depolarization was desensitized by repeated exposure to factors and was not observed in a representative nonlegume. A purified extracellular Nod factor, NodRm-IV(S), caused membrane potential depolarization at nanomolar concentrations. This rapid single-cell assay provides a tool for dissecting the mechanisms of host cell response in early nodulation.     

Plant biology. Enhanced: growth by auxin: when a weed needs acid

In his Perspective, Grebe discusses how a plant proton pump residing in intracellular compartments, rather than in the plasma membrane of the cell surface, regulates growth and development. The pump modulates the expression at the plasma membrane of both a transporter for the hormone auxin and another proton pump. These findings open new views on how plants regulate cell wall acidity and hormone transport during development.     

Amphiphysin 2 (Bin1) and T-tubule biogenesis in muscle

In striated muscle, the plasma membrane forms tubular invaginations (transverse tubules or T-tubules) that function in depolarization-contraction coupling. Caveolin-3 and amphiphysin were implicated in their biogenesis. Amphiphysin isoforms have a putative role in membrane deformation at endocytic sites. An isoform of amphiphysin 2 concentrated at T-tubules induced tubular plasma membrane invaginations when expressed in nonmuscle cells. This property required exon 10, a phosphoinositide-binding module. In developing myotubes, amphiphysin 2 and caveolin-3 segregated in tubular and vesicular portions of the T-tubule system, respectively. These findings support a role of the bilayer-deforming properties of amphiphysin at T-tubules and, more generally, a physiological role of amphiphysin in membrane deformation.     

高抗氧化活性lager型啤酒酵母选育

采用过氧化氢刺激lager型啤酒酵母,Tadpoling法筛选细胞活力恢复较快突变菌,根据各菌株线粒体膜电位、胞内氧自由基(ROS)水平筛选获得4株活性较高菌株。比较突变菌与原始菌传代发酵性能、胞内ROS、活力指标及每一代细胞死亡率水平,最终获得一株抗氧化能力提高且活力稳定性较高啤酒酵母菌株。分析验证突变菌线粒体DNA修复相关基因MHR1发现,该基因发生部分碱基突变。     

A spatial-temporal model of cell activation

A spatial-temporal model of calcium messenger function is proposed to account for sustained cellular responses to sustained stimuli, as well as for the persistent enhancement of cell responsiveness after removal of a stimulus, that is, cellular memory. According to this model, spatial separation of calcium function contributes to temporal separation of distinct phases of the cellular response. At different cellular sites, within successive temporal domains, the calcium messenger is generated by different mechanisms and has distinct molecular targets. In particular, prolonged cell activation is brought about by the interaction of calcium with another spatially confined messenger, diacylglycerol, to cause the association of protein kinase C with the plasma membrane. Activity of the membrane-associated protein kinase C is controlled by the rate of calcium cycling across the plasma membrane. In some instances, a single stimulus induces both protein kinase C activation and calcium cycling and thus causes prolonged activation; but in others, a close temporal association of distinct stimuli brings about cell activation via interaction of these intracellular messengers. Persistent enhancement of cell responsiveness after removal of stimuli is suggested to be due to the continued association, or anchoring, of protein kinase C to the membrane.     

膜分离技术在番茄汁浓缩工艺中的应用

膜分离技术由于具有结构简单、操作容易、无需加热、能耗低、速度快等特点,使其正广泛地应用于食品工业领域.介绍了膜分离原理及特点,并对管式反渗透、离心分离与卷式反渗透、陶瓷微滤与卷式反渗透、直接渗透浓缩四种类型的膜分离技术的优缺点及其在番茄酱加工工艺中的应用和发展方向作了概述,以期为改进膜分离技术在番茄汁浓缩工艺中的应用找到新的途径.     

Role of C. elegans TAT-1 protein in maintaining plasma membrane phosphatidylserine asymmetry

The asymmetrical distribution of phospholipids on the plasma membrane is critical for maintaining cell integrity and physiology and for regulating intracellular signaling and important cellular events such as clearance of apoptotic cells. How phospholipid asymmetry is established and maintained is not fully understood. We report that the Caenorhabditis elegans P-type adenosine triphosphatase homolog, TAT-1, is critical for maintaining cell surface asymmetry of phosphatidylserine (PS). In animals deficient in tat-1, PS is abnormally exposed on the cell surface, and normally living cells are randomly lost through a mechanism dependent on PSR-1, a PS-recognizing phagocyte receptor, and CED-1, which contributes to recognition and engulfment of apoptotic cells. Thus, tat-1 appears to function in preventing appearance of PS in the outer leaflet of plasma membrane, and ectopic exposure of PS on the cell surface may result in removal of living cells by neighboring phagocytes.     

归芪多糖延缓细胞衰老的分子作用机制

以SIRT1和线粒体为切入点,采用分子生物学技术以及多种线粒体分析技术,深入探讨SIRT1和线粒体在衰老细胞中的作用,揭示归芪多糖延缓细胞衰老的分子作用机制。结果表明,AAP显著降低细胞的衰老程度并提高细胞活力,而Ex527阻断AAP的作用。同时,发现AAP增强细胞内SIRT1和CyclinD1的表达,降低p53的表达水平,在Ex527组中未观察到类似的逆转作用。线粒体分析结果显示,AAP可显著降低细胞内的活性氧水平,降低线粒体膜电位,减轻线粒体肿胀程度和增加线粒体内ATP含量,而Ex527的预处理消除这些作用。基于上述结果,推测AAP可能通过信号通路p53/p16和CyclinD/CDK4来改善线粒体功能,从而达到延缓衰老的作用,且这些作用与SIRT1密切相关。