TMV侵染后的烟草细胞膜蛋白结构变化的研究

为探明病毒侵染对烟草细胞膜的损伤作用 ,采用圆二色波谱仪 (CD)分析了被 TMV侵染的烟草细胞膜蛋白结构的变化 ,以及右旋紫草素对感病烟草细胞膜的作用。结果发现 ,被 TMV侵染的烟草细胞膜蛋白分子二级结构发生变化 ,表现为 α-螺旋的减少和 β-转角的增加 ;用右旋紫草素处理的感病烟草细胞膜蛋白分子二级结构的变化 ,表现为药剂作用比感病样品的细胞膜蛋白的二级结构中 α-螺旋成分比例增加 ,而 β-转角比例相应减少。     

In-vitro biological models

Recent developments in the investigation of membrane flux and partition in in-vitro membrane systems from human and animal tissues are reviewed with an emphasis on three models: multicellular layers, single isolated cells and sub-cellular membrane fractions. Mechanisms of permeation through multicellular layers such as epithelia. endothelia and confluent layers of cultured cells by radio-tracer and electrophysiological techniques are considered. For single cells, erythrocytes form one of the major models, and their use, along with reseated ghosts and membrane vesicles, is considered, particularly with regard to the restoration of physiological levels of membrane permeability in the latter. The use of fluorescent intracellular dyes to measure partition into single identified cells dissociated from tissues is discussed. Methods of measuring flux and partition into subcellular fractions from plasma and organelle membranes are reviewed, in addition to new methods of patch clamping small areas of membrane to investigate permeation through single ion channels.     

Ultrastructure of the secondary osmoregulatory canals in the scolex and neck region of Silurotaenia siluri (Batsch, 1786) (Cestoda: Proteocephalidae)

The secondary osmoregulatory canals in the scolex and neck region of Silurotaenia siluri, a parasite of the catfish Silurus glanis (L.), terminate below the tegument basal plasma membrane. The basal plasma membrane of the osmoregulatory canal syncytium is in tight contact with the tegument basal plasma membrane.     

Action of R-40244 on chloroplast pigments and polar lipids

The herbicide R-40244 [1-(m-trifluoromethylphenyl)-3-chloro-4-chloromethyl-2-pyrrolidinone] blocked the accumulation of chloroplast pigments in cabbage (Brassica oleracea L.) and annual ryegrass (Lolium multiflorum L.). The total amount of polar (membrane) lipids synthesized and the proportion of unsaturated 18-carbon fatty acids were progressively reduced in shoots of annual ryegrass as the concentration of R-40244 increased from 1 to 100μM. Blocked chloroplast pigment accumulation and perturbations of membrane lipids were related to reduced growth of annual ryegrass. Growth and membrane lipids of cabbage were much less affected by R-40244. Light was not required for the action of R-40244 on membrane lipids. The combined data suggest that the accumulation of chloroplast pigments is blocked by R-40244 in all species sensitive to R-40244, but that species differ in sensitivity to action on membrane lipids. In sensitive species, where both pigments and membrane lipids are affected, the action on membrane lipids may limit growth independently of effects on pigments.     

The plasma membrane as a barrier to herbicide penetration and site for adjuvant action

Adjuvants are traditionally thought to exert their main effect on the cuticle or spray droplet to enhance foliar-applied herbicide penetration. However, considerable evidence exists indicating that the plasma membrane is a barrier to intracellular penetration of herbicides and a site of action for adjuvants. Surfactants may penetrate through the cuticle and into the region of the plasma membrane. Insertion into the membrane causes a general “ loosening” to provide greater penetration by highly polar herbicides such as glyphosate. Weak acid herbicides typically have a lipophilic moiety and, therefore, can move more easily through the membrane but the rate and accumulation is dependent on pH conditions across the membrane. Ammonium salts have been shown to affect the pH of the apoplast in a manner which allows faster penetration and greater accumulation of weak acid herbicides. Examination and understanding of the plasma membrane as a barrier to herbicide penetration will aid in defining the mechanisms of adjuvant action and improve the efficiency of agrochemical use.     

Kinetics of sodium channel modification as the basis for the variation in the nerve membrane effects of pyrethroids and DDT analogs

The effects of a wide range of pyrethroids and DDT analogs on the membrane potential and membrane sodium currents were studied in crayfish giant axons. Compounds differed greatly in their ability to produce depolarizing afterpotentials, repetitive firing, and membrane depolarization. The differences observed at the membrane potential level could be explained by differences in the kinetics with which the insecticides interact with the nerve membrane sodium channel. The compounds containing a cyano group at the α position retain sodium channels in a modified open state persistently, depolarize the membrane, and block the action potential without causing repetitive firing. The pyrethroids without an α-cyano group and DDT analogs retain sodium channels in a modified open state only transiently, cause large depolarizing afterpotentials, and evoke repetitive firing with minimal effect on the resting potential. The effects of the phenoxybenzyl pyrethroids were found to be intermediate between these two extremes suggesting that a continuous variation exists in kinetics with which pyrethroids and DDT analogs modify sodium channels. It was not necessary to assume a second site of action to account for the variability observed. The implications of these results to the construction of quantitative structure-activity relationships is discussed.     

‘Pharmacokinetic’ and ‘pharmacodynamic’ design of lipophilic drugs based on a structural model for drug interactions with biological membranes

The pharmacokinetic profile a drug exhibits will ultimately depend on how the drug molecule interacts with the different cell membranes it encounters en route to its target site of action. Even if the drug molecule targets a soluble protein as its final site of action, there is a reasonable probability that it will interact with some cell membrane on its pathway to this biological target. In some cases, the final protein, lipid or sugar moiety target could be an integral part of the cell membrane architecture whereby the drug's interaction with the cell membrane could influence its pharmacodynamic profile as well, especially if the final site of action is an integral membrane-bound receptor protein. In either case, drug transport across a cell membrane or within the cell membrane lipid bilayer compartment can dictate partial or dominant control of the drug's bioavailability. A molecular understanding of the equilibrium membrane partition coefficient, the rates of drug partitioning into and out of a cell membrane and the equilibrium location of the drug within the cell membrane can provide critical chemical design strategies for altering overall drug bioavailability and optimal pharmacokinetics.     

Review—mechanism of action of herbicidal and fungicidal compounds on cell membranes

The eukaryotic cell membrane is thought to consist of a mobile bilayer of phospholipid, sometimes intercalated with sterols, in which peripheral and transmembrane proteins are embedded. This provides a model whereby the mode of action of many fungicidal and herbicidal compounds can be rationalised and understood. Some compounds, such as the polyene antibiotics, steroidal saponins and certain phytoalexins, induce membrane malfunction by direct insertion, often complexing with vital components. Others, such as paraquat and the nitrodiphenyl ether herbicides, cause membrane damage by inducing lipid peroxidations. Furthermore, there are many compounds, including the sterol-biosynthesis-inhibiting fungicides and the aryloxyphenoxypropionate and cyclohexanedione herbicides, which interfere with the biosynthesis of membrane components. Because membrane structure is fundamentally similar in eukaryotes, it is important to discover the reasons for any differential toxicity displayed by these compounds and, if necessary, to find ways of optimising desirable patterns of selectivity.     

天然化合物丁香酚对灰葡萄孢菌丝脂质过氧化和膜损伤的影响

研究了天然化合物丁香酚对灰葡萄孢菌丝细胞膜的影响。结果表明,丁香酚可以作用于真菌的膜系统,诱导菌丝膜脂质过氧化,使膜受到损伤,透性改变,丙二醛(MDA)流出细胞。进一步研究发现,丁香酚处理使得菌丝内过氧化氢含量逐渐升高;菌丝内钙离子浓度先升高,30 min后逐渐下降,这可能是由于细胞膜破损导致钙离子外流的缘故。同时,通过DNA梯状条带的检测,初步表明丁香酚不能诱导灰葡萄孢菌丝细胞凋亡。     

Induced hydrogen ion transport in lipid membranes as origin of toxic effect of pentachlorophenol in an alga

Pentachlorophenol (PCP) decreases the rate of carbon assimilation in the alga Selenastrum capricornutum. In parallel with the reduction of carbon assimilation in this alga there is a decrease of electrical resistance of lipid membranes and development of negative membrane surface charge. The experimental results suggest that PCP toxicity to algae is due to adsorption of negatively charged PCP ions at the membrane surface that act as carriers of hydrogen ion across the membrane. This protonophoretic action of PCP causes the decrease of membrane electrical resistance and the dissipation of hydrogen ion electrochemical potential gradients across cellular and subcellular membranes, which reduces the ability of algae to assimilate carbon.     

Reactive oxygen species (ROS) generation and ROS-induced lipid peroxidation are associated with plasma membrane modifications in host cells in response to AK-toxin I from Alternaria alternata Japanese pear pathotype

AK-toxin I caused plasma membrane modifications with plasma membrane-derived membrane fragments only in sensitive Japanese pear tissues. H₂O₂ generation was abundant in both the membrane fragments and the plasma membranes of the toxin-treated sensitive tissues. Whether lipid peroxidation was induced in plasma membranes of the toxin-treated sensitive tissues was examined biochemically and histochemically. Lipid peroxidation was caused only in the toxin-treated sensitive tissues or the toxin-treated plasma membrane-enriched fractions from sensitive young pear fruits. The results indicated that the peroxidation was probably induced by reactive oxygen species in the modified plasma membranes by action of toxin, suggesting that peroxidation is closely associated with plasma membrane modifications.     

A new model membrane system for the investigation of penetrative properties of plant growth substances

A new model membrane system has been developed which simulates in many ways the behaviour of a plant cell membrane. It is very suitable for studying the penetration and associated effects of plant growth substances because of its large size (4.9±0.3 cm²), its ease of preparation and its reproducible properties. It consists of a Millipore filter disc impregnated with egg yolk lecithin, n-octanol and n-tetradecane. The effect of a number of plant growth and allied compounds on membrane conductivity at 25±0.5°c has been assessed by the addition of various concentrations of these substances to the solutions (0.01 M-NaCl) on each side of the membrane. Certain compounds present in the solutions (pH 3.0) in the concentration range 10^?4 M to 10^?3 M considerably reduced the membrane conductivity. This effect was seen to be related to the structure of the hydrophobic portion of the molecule. The flux through the membrane at 25±0.5°c of various organic substances (2,4-D, benzoic acid, benzyl alcohol, benzamide and benzaldehyde) was measured for membranes containing no lecithin and compared with the flux obtained in comparable experiments, with lecithin present in the membrane. The presence of lecithin increased the flux, and the percentage increase was used to assess in each case the part played by lecithin in transport. The flux of 2,4-D was much greater at low pH values. A possible interpretation of these phenomena is suggested.     

AM真菌和镰刀菌对西瓜根系膜脂过氧化作用和膜透性的影响

 在温室盆栽条件下研究了丛枝菌根(arbuscular mycorrhiza,AM)真菌Glomus versiforme (Karsten) Berch和西瓜枯萎镰刀菌(Fusarium oxysporum f. sp. niveum)对西瓜根系中膜脂过氧化产物丙二醛(MDA)含量和细胞膜透性的影响。结果表明,接种AM真菌的西瓜根系中MDA含量、组织自动氧化速率和膜透性均低于对照,先接种G. versiforme,后接种F. oxysporum f. sp. niveum处理的MDA含量、组织自动氧化速率和细胞膜透性均低于只接种F. oxysporum f. sp. niveum的处理。接种G. versiforme感枯萎病西瓜品种"郑杂5号"MDA含量、组织自动氧化速率和膜透性降低幅度大于抗病品种"京欣1号"的接种处理,说明G. versiforme可降低感病西瓜品种的膜透性和MDA的产生,从而有效地保护细胞膜系统,减轻F. oxysporum f. sp. niveum对西瓜的为害程度。     

Effect of herbicides on cell membrane permeabUity in Lemna minor

Leakage of electrolytes was the criterion used to study the effects of several herbicides on cell membrane permeability in Lemna minor L. Dinoseb. sodium azide, linuron, prometryne and simazine were the most active in increasing cell membrane permeability, followed by oxyfluorfen, amitrole, and 2,4—D. Glyphosate and dalapon were the least active. In all cases, the longer the period elapsed after treatment (i.e. 96 h) the lower was the concentration needed to alter cell membrane permeability. Light was necessary for oxyfluorfen activity. With glyphosate, dalapon and oxyfluorfen, visible injury symptoms were noted after 48–96 h, but no further significant increase in cell membrane permeability occurred as a result.     

Electron microscope observations of nuclear polyhedra fromMalacosoma neustria (Lepidoptera: Lasiocampidae

The nuclear polyhedral bodies fromMalacosoma neustria are enclosed within a membrane. The diameter of the nuclear polyhedra varies from 0.9 to 2.8 with an average of 1.8 . In the nuclear polyhedra the rod-like virus particles occur both singly and in bundles. The single virus rods are enclosed within two membranes, namely the intimate membrane and the developmental membrane. The virus rods which occur in bundles have an intimate membrane just like the single virus rods, whereas the developmental membrane encloses the whole bundle. The virus rods are closely packed by the intimate membrane and between the intimate and the developmental membrane is a space. The diameter of the virus rods without membranes, determined from sectioned polyhedra, is about 25 m and the length 250 m.     

Action of chlorfenprop-methyl on membrane integrity in plant mitochondria

The action of chlorfenprop-methyl, chlorfenprop and its cysteine conjugate was studied on potato tuber mitochondria. Chlorfenprop-methyl altered membrane structure at 250 μM. leading to a loss of membrane integrity. Chlorfenprop and its cysteine conjugate were without any significant effects. From what is known about the rapid hydrolysis of chlorfenprop-methyl in plant tissues and from the results presented in this paper, it was deduced that alteration in intra-cellular membrane integrity is not a mechanism of phytotoxic action for chlorfenprop-methyl.     

Subcellular localization of the protein encoded by virulence gene <Emphasis Type="Italic">psvA</Emphasis> of <Emphasis Type="Italic">Pseudomonas syringae</Emphasis> pv. <Emphasis Type="Italic">eriobotryae</Emphasis>

The plasmid-encoded virulence gene psvA was previously isolated from Pseudomonas syringae pv. eriobotryae and sequenced. The deduced protein of the psvA gene had no significant similarity to any other protein sequences in the database. To gain a better understanding of the function of the PsvA protein its subcellular localization was examined. To localize the PsvA protein within the bacteria, the cells were fractionated into cytoplasmic, inner membrane, and outer membrane components. The cell fractions and culture supernatant were analyzed by immunoblotting. The PsvA protein was predominantly detected in the outer membrane fraction. Immunoelectron microscopy also showed that the PsvA protein was located in the outer membrane.     

盐胁迫对大果沙枣膜脂过氧化和保护酶活性的影响

用50,100,200,300 mmol／L NaCl处理大果沙枣,NaCl胁迫10,20,30d后取叶样测定结果显示：处理10d的大果沙枣叶片细胞膜透性保持稳定,随盐浓度的增加及胁迫时间的延长,叶片细胞膜透性逐渐增加。NaCl胁迫30d时,300mmol／L NaCl胁迫的叶片膜透性达到68.8％。整个处理过程中,丙二醛含量逐渐增加,但增加幅度不大,表明脂质过氧化反应水平较低。各处理浓度的SOD和POD活性整体上呈增加趋势,其中NaCl胁迫10d和30d,胁迫浓度50mmol／L时其活性达到最大值。另外,SOD和POD活性随着时间的延长有所降低,CAT活性则一直增加。     

水分胁迫对柽柳组织含水量和膜透性的影响

甘蒙柽柳（ＴａｍａｒｉｘａｕｓｔｒｏｍｏｎｇｏｌｉｃａＮａｋａｉ）、多枝柽柳 （Ｔ．ｒａｍｏｓｉｓｓｉｍａＬｅｄｅｂ．）中国柽柳（Ｔ．ｃｈｉ－ｎｅｎｓｉｓＬｏｕｒ）短穗柽柳（ＴｌａｘａＷｉｌｄ．）刚毛柽柳（Ｔ．ｈｉｓｐｉｄａＷｉｌｄ．）密花柽柳（Ｔ．ａｒｃｅｕｔｈｏｉｄｓＢｇｅ．）甘柽柳（Ｔ．ｇａｎｓｕｅｎｓｉｓＨ．Ｚ．Ｚ．Ｚｈａｎｇ）和短毛柽柳（Ｔ．ｋａｒｅｌｉｎｉＢｇｅ．）在土壤缓慢水分胁迫条     

An in vitro feeding assay to test acaricides for control of hard ticks

Animal husbandry could not be practised over large areas of the planet without acaricides. The prevention of tick bite and the transmission of diseases requires the use of pesticides, but this contributes to the development of tick resistance against acaricides. This drives the quest for new molecules that target physiological processes crucial to tick survival. In vivo trials involve multiple repetitions because of inherent variations between host animals, requiring large amounts of test products and ticks. An in vitro alternative should permit the testing of the ability of a product to restrict attachment and feeding by ticks at precise doses. In this paper an in vitro feeding system is described where the European tick Ixodes ricinus L. feeds on blood through a cellulose rayon-reinforced silicone membrane. The membrane Shore hardness is modified to imitate the elastic retraction forces of skin that ensure the closing of tick penetration sites on the membrane to prevent bleeding. Tick attachment (75-100%) is achieved by adding chemical and mechanical stimuli to the membrane. Survival curves for different doses of fipronil and ivermectin tested with the method showed highly reproducible acaricide effects within 5-7 days. Significant effects are recorded down to ppb levels in blood. Standardised tests can be made with blood from the same donor animal or culture medium under the membrane.