Internalization of gap junctions between neuron and glial cell and formation of annular lamellar bodies in Chinese leech Whitmania pigra

This paper reveals the formation of annular lamellar body (ALB) in the ganglion of leech by means of in situ fixation and the lanthanum nitrate tracer technique. This formation involves both wrapping and internalization of the gap junctions between glial processes themselves, as well as between neuron and glial process. The results indicate that there is probably an active process of internalization of membrane structures involving gap junctions between neuron and glial cell in the central nervous system in leech. The functions of ALB are discussed.     

THE MORPHOLOGICAL SIMILARITY AND SYMMETRY OF NEURONES IN THE LEECH Whitmania pigra

Using the method of intracellular injection of horseradish peroxidase, the arborizations of several neurones with different functions in the segmental ganglia of the leech Whitmania pigra are investigated. Comparison is made in each kind of neurones in order to verify their typical pattern. Results show that the morphology of the axonal arbors of identified neurones has an accurate similarity within and among the individuals of the leech, and the axonal arborizations of the bilaterally identified neurones in the same ganglion have a stable symmetry. The possible reasons of the formation and its functional significance of the symmetrical nervous system are discussed.     

Tight junction development between cultured hepatoma cells: possible stages in assembly and enhancement with dexamethasone.

Freeze-fracture and thin-section methods were used to study tight junction formation between confluent H4-II-E hepatoma cells that were plated in monolayer culture in media with and without dexamethasone, a synthetic glucocorticoid. Three presumptive stages in the genesis of tight junctions were suggested by these studies: 1) "formation zones" (smooth P-fracture face ridges deficient in intramembranous particles), apparently matched across a partially reduced extracellular space, develop between adjacent cells; 2) linear strands and aggregates of 9--11 nm particles collect along the ridges of the formation zones. The extracellular space was always reduced when these structures were found matched with pits in gentle E-face depressions; 3) the linear arrays of particles on the ridges associate within the membranes to form the fibrils characteristic of mature tight junctions. The formation zones resemble tight junctions in terms of size, complexity and the patterns of membrane ridges. Although some of the beaded particle specializations may actually be gap junctions, it is unlikely that all can be interpreted in this way. No other membrane structures were detected that could represent developmental stages of tight junctions. Dexamethasone (at 2 x 10(-6)M) apparently stimulated formation of tight junctions. Treated cultures had a greater number of formation zones and mature tight junctions, although no differences in qualitative features of the junctions were noted.     

Primary cultures of chick osteocytes retain functional gap junctions between osteocytes and between osteocytes and osteoblasts.

The inaccessibility of osteocytes due to their embedment in the calcified bone matrix in vivo has precluded direct demonstration that osteocytes use gap junctions as a means of intercellular communication. In this article, we report successfully isolating primary cultures of osteocytes from chick calvaria, and, using anti-connexin 43 immunocytochemistry, demonstrate gap junction distribution to be comparable to that found in vivo. Next, we demonstrate the functionality of the gap junctions by (1) dye coupling studies that showed the spread of microinjected Lucifer Yellow from osteoblast to osteocyte and between adjacent osteocytes and (2) analysis of fluorescence replacement after photobleaching (FRAP), in which photobleaching of cells loaded with a membrane-permeable dye resulted in rapid recovery of fluorescence into the photobleached osteocyte, within 5 min postbleaching. This FRAP effect did not occur when cells were treated with a gap junction blocker (18alpha-glycyrrhetinic acid), but replacement of fluorescence into the photobleached cell resumed when it was removed. These studies demonstrate that gap junctions are responsible for intercellular communication between adjacent osteocytes and between osteoblasts and osteocytes. This role is consistent with the ability of osteocytes to respond to and transmit signals over long distances while embedded in a calcified matrix.     

Gap size dependent transition from direct tunneling to field emission in single molecule junctions

I/V characteristics recorded in mechanically controllable break junctions revealed that field emission transport is enhanced in single molecule junctions as the gap size between two nanoelectrodes is reduced. This observation indicates that Fowler-Nordheim tunneling occurs not only for intermolecular but also for intramolecular electron transport driven by a reduced energy barrier at short tunneling distances.     

Gap junctions and ACTH sensitivity in Y-1 adrenal tumor cells.

Initial studies of adrenocorticotropin-sensitivity (ACTH-sensitive) and ACTH-insensitive Y-1 adrenal cortical tumor cell lines suggest a relationship between responsiveness to ACTH and the presence of gap junctions. An ACTH-sensitive clone of Y-1 cells possesses gap junctions and these junctions appear to enlarge with ACTH treatment. GAP junctions have not been observed, however, in an ACTH-insensitive clone of Y-1 tumor cells even when stimulated to produce cyclic adenosine monophosphate and steroids with cholera toxin.     

Photodynamic effect of hypericin and a water-soluble derivative on isolated crayfish neuron and surrounding glial cells

Hypericin (Hyp) has been proposed as a fluorochrome for fluorescence diagnostics and as a photosensitizer for photodynamic therapy of cancer. However, its insolubility in water is a serious drawback. A novel water-soluble hypericin derivative (Hyp-S) has been constructed, using polyvinylpyrrolidone as a carrier. We used the crayfish stretch receptor, consisting of receptor neuron and satellite glial cells, for comparison of the photodynamic effects of Hyp and Hyp-S. Hyp-S was more toxic in the dark than Hyp and inactivated the neurons at concentrations exceeding 4 microM while Hyp was toxic to the neurons only at the concentrations larger than 20 microM. Electrophysiological investigations revealed polyphasic neuron responses to photosensitization with Hyp as well as with Hyp-S (1 microM concentration, 30 min incubation; irradiation with filtered light from a lamp with an emission maximum near 600 nm and an intensity of 0.2 W/cm2). In the concentration range 1-4 microM Hyp-S was more phototoxic than Hyp. Fluorescence microscopy showed that both sensitizers were predominately localized in the glial envelope surrounding the neuron. A minor fraction of hypericin was found in the neuron perinuclear area rich in cytoplasm organelles. This suggests the potential application of Hyp and Hyp-S for visualization and selective photodynamic treatment of malignant gliomas.     

Functional Molecular Junctions Derived from Double Self‐Assembled Monolayers

Information processing using molecular junctions is becoming more important as devices are miniaturized to the nanoscale. Herein, we report functional molecular junctions derived from double self‐assembled monolayers (SAMs) intercalated between soft graphene electrodes. Newly assembled molecular junctions are fabricated by placing a molecular SAM/(top) electrode on another molecular SAM/(bottom) electrode by using a contact‐assembly technique. Double SAMs can provide tunneling conjugation across the van der Waals gap between the terminals of each monolayer and exhibit new electrical functions. Robust contact‐assembled molecular junctions can act as platforms for the development of equivalent contact molecular junctions between top and bottom electrodes, which can be applied independently to different kinds of molecules to enhance either the structural complexity or the assembly properties of molecules.     

A new strategy for neurochemical photodelivery: metal-ligand heterolytic cleavage

A new strategy to build caged-compounds is presented. The approach is based on heterolytic photocleavage of a metal-ligand bond in a coordination compound. A ruthenium polypyridine complex, containing the neurocompound 4-amino pyridine (4AP) is used as the core of the phototrigger. The biomolecule is released by irradiation with visible light (>480 nm). The liberated 4AP promotes the activation of a leech neuron by means of blocking its K+ channels. The syntesis, characterization, and the inherent advantages of this method are discussed.     

RE-DEVELOPMENT OF SYNAPTIC CONNECTIONS AFTER IMPLANTED SINGLE 5-HT CONTAINING NEURON IN ISOLATED LEECH GANGLIA

Single mature Retzius cells which contain 5-HT have been implanted in isolated ganglia of Whitmania pigra. The properties of the implanted Retzius cell and its connections with the original identified nerve cells of the ganglia have been measured by intracellular microelectrodes. At 3 days in culture an implanted Retzius cell maintains its normal electrical membrane properties. It also forms the non-rectifying electronic coupling with the original Retzius cell and rectifying junctions with the L motor neuron of the host ganglion. In addition it receives chemical inputs of the impulse from T and N sensory neurons of ganglion. Impulses in the implanted Retzius cell evoke synaptic potentials in the L motor neuron, In this paper the appearance of novel synapses, which are formed by implanting an extra mature neuron as a pre- or post-synaptic element, is described. It might represent functional development of central nervous system at an earlier stage.     

LATERAL CAPILLARY FORCES AND TWO-DIMENSIONA ARRAYS OF COLLOID PARTICLES AND PROTEIN MOLECULES

This paper presents a review of our recent studies on the lateral capillary forces and on their role in the formation of two-dimensional ordered arrays of colloidal particles or protein molecules. To reveal the mechanism of protein ordering in liquid films we carried out model experiments with micrometer sized latex particles. The films were formed on solid or liquid substrates. By variation of the electrolyte concentration, the particle charge and volume fraction we proved that neither the double layer repulsion, nor the van der Waals attraction between the particles, was responsible for the formation of the two-dimensional arrays. Direct microscope observations revealed that the process of ordering was triggered by attractive lateral capillary forces due to the overlap of the menisci formed around the particles. Two types of lateral capillary forces, flotation and immersion, could be distinguished and theory of these interactions was developed. The lateral capillary forces between a floating particle and a wall were also studied; they could be employed for precise determination of the shear surface viscosity.     

添加剂对PVDF相转化过程及膜孔结构的影响

研究了PVP、PEG及LiCl 3种成孔添加剂下PVDF DMAc H2 O 添加剂体系的成膜机理 .无论那种添加剂的铸膜液相转换成膜过程中都存在凝胶分相和液液分相两种相变方式 ,在 30～ 6 0℃时凝胶分相在较低的非溶剂浓度下先于液液分相发生 ,LiCl作为添加剂较PEG、PVP对铸膜液有较强的致凝胶作用 ,成膜过程中凝胶分相段时间依PVP、PEG、LiCl的顺序延长 ,导致液液分相初始分相点处聚合物浓度增大 ,阻止了大孔结构的充分发展 .制得的膜依PVP、PEG、LiCl的顺序有效孔隙率和通量降低 ,结晶度升高 .以LiCl为添加剂制得的膜几乎不改变PVDF膜的疏水性 ,而以PVP或PEG为添加剂的膜隔水压差降低约 2 0kPa .     

供体-受体型共轭聚合物电子结构和导电性能的理论设计

以苯并[1,2-c:4,5-c']二[1,2,5]噻重氮和吡嗪并[2,3-g]喹喔啉为电子受体(A),噻吩、噻吩并[3,2-b]噻吩和二噻吩并[2,3-b:2',3'-d]噻吩为电子供体(D),设计了6种D-A型共轭聚合物.采用B3LYP方法,研究了这6种聚合物的几何结构和电子性质.D-A型共轭聚合物的几何结构和电子结构与电子供体和电子受体的性质,特别是与其提供电子和接受电子的能力密切相关.聚合物的能隙主要受键长交替控制,键长交替越小,能隙越窄.所设计的6种聚合物中,p-BBT-TT具有较窄的能隙(0.48 eV)、较小的载流子有效质量和相对较大的能带宽度,具备理论上的良好导电性能,可能是潜在的优良导电聚合物材料.     

彩色胶片与数字照相的成像效率分析及对其未来的预测

本文作者曾经通过评估成像效率的当前状态和理论极限之间的差距以及分析产生此差距的原因预测过卤化银照相材料的未来发展.本文描述了采用上述的方法来评估和分析彩色胶片与数字照相的现状.经预测在未来前者成像效率的改进余地会远大于后者.     

Internalization of Foreign Ions into Meta-stable Lattices:a Case Study of Transition-metal-doped Brookite

The connections between the building units of meta-stable lattice were generally considered to be easily disturbed during the doping process, causing serious hindrances blocking the development of functional doped materials. In this work, the synthesis of doped brookite, a typical meta-stable phase of TiO_2, has been explored novelly by in-situ adding of cations of VIIIB and IB,IIB elements in the 3rd period(Fe, Co, Ni, Cu, Zn) during the urea-lactate aided low-basicity hydrothermal process. The results showed that only Cu-doped brookite could be successfully synthesized with trace amount of copper intensively internalized into the brookite lattice, while the other dopants lead to the formation of anatase TiO_2. Extensive characterizations indicated a two-step doping process, where copper ions were firstly dispersed in an amorphous layer on the lattice surface and then they were internalized into brookite lattice. Cu-doped brookite exhibited significantly enhanced photocatalytic activity in the phenol degradation under visible light compared to bare brookite. The enhancement of catalytic performance was assigned to the impurity band gap and the reduction of charge carriers' recombination introduced by the internalization of Cu ions. The investigation reported herein contributes to the understanding of complex ion-doping effects on the structures of meta-stable materials, and provides hints for obtaining other functional doped materials.     

芴与噻吩发光共聚物的合成及其电致发光性能

采用Suzuki偶合方法合成出了一系列新型的 9,9 二辛基芴 (DOF)和噻吩 (Th)的共聚物 .其中 ,DOF与Th的投料比 (摩尔比 )分别为 95∶5 (PTF5 )、90∶1 0 (PTF1 0 )、85∶1 5 (PTF1 5 )、70∶3 0 (PTF3 0 )、5 0∶5 0 (PTF5 0 ) .所有的聚合物均可溶于常用的有机溶剂 ,如THF,CHCl3等 ,其分子量在 60 0 0～ 5 3 0 0 0之间 .当在聚芴主链中引入噻吩后 ,其发光波长发生了红移 ,最大发光波长由PTF5时的 490nm红移到PTF5 0时的 5 41nm .随着聚芴主链中噻吩含量的增加 ,最大电致发光和光致发光效率都逐渐降低 由这些聚合物所制得的器件 ,最大电致发光效率为PTF5和PTF1 0的 0 45 %.由此表明 ,在聚芴主链中引入少量的低带隙单体噻吩可以调节聚芴的发光颜色及发光效率     

Inelastic tunneling spectroscopy of gold-thiol and gold-thiolate interfaces in molecular junctions: The role of hydrogen

It is widely believed that when a molecule with thiol (S-H) end groups bridges a pair of gold electrodes, the S atoms bond to the gold and the thiol H atoms detach from the molecule. However, little is known regarding the details of this process, its time scale, and whether molecules with and without thiol hydrogen atoms can coexist in molecular junctions. Here, we explore theoretically how inelastic tunneling spectroscopy (IETS) can shed light on these issues. We present calculations of the geometries, low bias conductances, and IETS of propanedithiol and propanedithiolate molecular junctions with gold electrodes. We show that IETS can distinguish between junctions with molecules having no, one, or two thiol hydrogen atoms. We find that in most cases, the single-molecule junctions in the IETS experiment of Hihath et al. [Nano Lett. 8, 1673 (2008)] had no thiol H atoms, but that a molecule with a single thiol H atom may have bridged their junction occasionally. We also consider the evolution of the IETS spectrum as a gold STM tip approaches the intact S-H group at the end of a molecule bound at its other end to a second electrode. We predict the frequency of a vibrational mode of the thiol H atom to increase by a factor ～2 as the gap between the tip and molecule narrows. Therefore, IETS should be able to track the approach of the tip towards the thiol group of the molecule and detect the detachment of the thiol H atom from the molecule when it occurs.     

辽河渣油热转化和加氢裂化过程中生焦行为的研究

考察了辽河渣油热转化和浆液床催化加氢反应过程中生焦行为。研究生焦趋势与渣油物理化学组成的关系，初期生焦机制及其对后生焦的影响，并用高倍显微镜、傅立叶变换红外光谱技术对所生焦进行表征，结果发现，随加工苛刻度的增加，反应体系中生成的焦油细分散向簇状分散过渡、实姓焦对后期生焦有一定促进作用，在低压热转化过程中更为显著，生焦趋势不仅与反应条件有关而且与渣油物理化学性质相关，还与反应物系对生焦先躯物的胶溶能     

聚苯乙烯乳胶球三维有序体的制备及其显微形貌表征

A three-dimensional (3D) ordered structure was achieved by self-organization of monodisperse polystyrene latex about 250nm in diameter after being ambient dried. The stacked morphology was investigated by scanning electron microscopy(SEM) observation. It is shown that the face-centered cubic(FCC) phase dominantly exists. This finding presents a potential template for preparing an inverse FCC structure as a photonic crystal of full band gap if the index contrast is higher than 2.8.     

Length‐Dependent Conductance of Molecular Wires and Contact Resistance in Metal–Molecule–Metal Junctions

Molecular wires are covalently bonded to gold electrodes—to form metal–molecule–metal junctions—by functionalizing each end with a ? SH group. The conductance of a wide variety of molecular junctions is studied theoretically by using first‐principles density functional theory (DFT) combined with the nonequilibrium Green′s function (NEGF) formalism. Based on the chain‐length‐dependent conductance of the series of molecular wires, the attenuation factor β is obtained and compared with the experimental data. The β value is quantitatively correlated to the molecular HOMO–LUMO gap. Coupling between the metallic electrode and the molecular bridge plays an important role in electron transport. A contact resistance of 6.0±2.0 KΩ is obtained by extrapolating the molecular‐bridge length to zero. This value is of the same magnitude as the quantum resistance.