Defense strategies against hypoxia and hypothermia

Because aerobic metabolic rates decrease in hypoxia-sensitive cells under oxygen-limiting conditions, the demand for glucose or glycogen for anaerobic glycolysis may rise drastically as a means of making up for the energetic shortfall. However, ion and electrical potentials typically cannot be sustained because of energy insufficiency and high membrane permeabilities; therefore metabolic and membrane functions in effect become decoupled. In hypoxia-tolerant animals, these problems are resolved through a number of biochemical and physiological mechanisms; of these metabolic arrest and stabilized membrane functions are the most effective strategies for extending tolerance to hypoxia. Metabolic arrest is achieved by means of a reversed or negative Pasteur effect (reduced or unchanging glycolytic flux at reduced O2 availability); and coupling of metabolic and membrane function is achievable, in spite of the lower energy turnover rates, by maintaining membranes of low permeability (probably via reduced densities of ion-specific channels). The possibility of combining metabolic arrest with channel arrest has been recognized as an intervention strategy. To date, the success of this strategy has been minimal, mainly because depression of metabolism through cold is the usual arrest mechanism used, and hypothermia in itself perturbs controlled cell function in most endotherms.     

Spatially resolved calcium dynamics of mammalian Purkinje cells in cerebellar slice

Microfluorometric imaging was used to study the correlation of intracellular calcium concentration with voltage-dependent electrical activity in guinea pig cerebellar Purkinje cells. The spatiotemporal dynamics of intracellular calcium concentration are demonstrated during spontaneous and evoked activity. The results are in agreement with hypotheses of dendritic segregation of calcium conductances suggested by electrophysiological experiments. These in vitro slice fluorescence imaging methods are applicable to a wide range of problems in central nervous system biochemical and electrophysiological functions.     

植物水通道蛋白的结构特征及其表达调控

水是生物体的主要组成部分,水在细胞和组织间的进出是所有生物代谢的基础。水通道蛋白形成选择性运输水、小分子溶质及气体的膜通道,在植物生长发育过程中起重要的作用。基因所编码蛋白的结构特征及其表达调控与其行使的功能密切相关。随着越来越多的水通道蛋白基因在高等植物中发现,人们对其结构、调控和功能有了更多了解。就水通道蛋白的分子结构以及表达调控方面的研究进展进行了概述。     

Cloning of a membrane protein that induces a slow voltage-gated potassium current

A rat kidney messenger RNA that induces a slowly activating, voltage-dependent potassium current on its expression in Xenopus oocytes was identified by combining molecular cloning with an electrophysiological assay. The cloned complementary DNA encodes a novel membrane protein that consists of 130 amino acids with a single putative transmembrane domain. This protein differs from the known ion channel proteins but is involved in the induction of selective permeation of potassium ions by membrane depolarization.     

昆虫离子通道及抗性的研究进展

对钠、氯、钾和钙离子通道的结构、药理、分子抗性及基因调控机理的研究进展进行了综述，认为研究昆虫离子通道对于害虫抗性治理和开发新农药具有重要意义。     

Glass Insulated Platinum Microelectrode

Microelectrodes for electrophysiological use have been prepared easily and quickly by electrolytically sharpening platinum iridium alloy wire and coating with molten glass. The desirable combination of the electrical characteristics and strength of the platinum iridium wire with the exceptional durability of glass insulation has long been known, but earlier methods of fabrication were difficult and tedious.     

海葵多肽类神经毒素的结构与药理学功能

海葵以其触手刺细胞中的毒液行使捕食和防御功能,其毒液中富含各种多肽类神经毒素,分子量为3—7kDa之间,分子序列中含多对二硫键以稳定其结构。海葵神经毒素以钠离子通道毒素和钾离子通道毒素为其主要成分,此外还发现有作用于其他离子通道的成分,此外,还有部分海葵毒素目前尚不清楚其分子靶标。不同类型的海葵毒素具有不同的空间结构。海葵毒素多肽的分子多样性使其成为动物毒素研究的一个重要分支,同时海葵多肽毒素对不同离子通道的特异性和高亲和性,使得它们成为神经生理学和药理学研究的一种重要工具。     

1990: annus mirabilis of potassium channels

Voltage-gated potassium channels make up a large molecular family of integral membrane proteins that are fundamentally involved in the generation of bioelectric signals such as nerve impulses. These proteins span the cell membrane, forming potassium-selective pores that are rapidly switched open or closed by changes in membrane voltage. After the cloning of the first potassium channel over 3 years ago, recombinant DNA manipulation of potassium channel genes is now leading to a molecular understanding of potassium channel behavior. During the past year, functional domains responsible for channel gating and potassium selectivity have been identified, and detailed structural pictures underlying these functions are beginning to emerge.     

The molecular basis of neuronal excitability

Neurons process and transmit information in the form of electrical signals. Their electrical excitability is due to the presence of voltage-sensitive ion channels in the neuronal plasma membrane. In recent years, the voltage-sensitive sodium channel of mammalian brain has become the first of these important neuronal components to be studied at the molecular level. This article describes the distribution of sodium channels among the functional compartments of the neuron and reviews work leading to the identification, purification, and characterization of this membrane glycoprotein.     

Spin Hall effect transistor

The field of semiconductor spintronics explores spin-related quantum relativistic phenomena in solid-state systems. Spin transistors and spin Hall effects have been two separate leading directions of research in this field. We have combined the two directions by realizing an all-semiconductor spin Hall effect transistor. The device uses diffusive transport and operates without electrical current in the active part of the transistor. We demonstrate a spin AND logic function in a semiconductor channel with two gates. Our study shows the utility of the spin Hall effect in a microelectronic device geometry, realizes the spin transistor with electrical detection directly along the gated semiconductor channel, and provides an experimental tool for exploring spin Hall and spin precession phenomena in an electrically tunable semiconductor layer.     

Crystal structure of a mammalian voltage-dependent Shaker family K+ channel

Voltage-dependent potassium ion (K+) channels (Kv channels) conduct K+ ions across the cell membrane in response to changes in the membrane voltage, thereby regulating neuronal excitability by modulating the shape and frequency of action potentials. Here we report the crystal structure, at a resolution of 2.9 angstroms, of a mammalian Kv channel, Kv1.2, which is a member of the Shaker K+ channel family. This structure is in complex with an oxido-reductase beta subunit of the kind that can regulate mammalian Kv channels in their native cell environment. The activation gate of the pore is open. Large side portals communicate between the pore and the cytoplasm. Electrostatic properties of the side portals and positions of the T1 domain and beta subunit are consistent with electrophysiological studies of inactivation gating and with the possibility of K+ channel regulation by the beta subunit.     

A mechanosensitive ion channel in the yeast plasma membrane

Mechanosensitive ion channels use mechanical energy to gate the dissipation of electrochemical gradients across cell membranes. This function is fundamental to physiological processes such as hearing and touch. In electrophysiological studies of ion channels in the plasma membrane of the yeast Saccharomyces cerevisiae, channels were observed that were activated by, and adapted to, stretching of the membrane. Adaptation of channel activity to mechanical stimuli was voltage-dependent. Because these mechanosensitive channels pass both cations and anions, they may play a role in turgor regulation in this walled organism.     

Structure and function of voltage-sensitive ion channels

Voltage-sensitive ion channels mediate action potentials in electrically excitable cells and play important roles in signal transduction in other cell types. In the past several years, their protein components have been identified, isolated, and restored to functional form in the purified state. Na+ and Ca2+ channels consist of a principal transmembrane subunit, which forms the ion-conducting pore and is expressed with a variable number of associated subunits in different cell types. The principal subunits of voltage-sensitive Na+, Ca2+, and K+ channels are homologous members of a gene family. Models relating the primary structures of these principal subunits to their functional properties have been proposed, and experimental results have begun to define a functional map of these proteins. Coordinated application of biochemical, biophysical, and molecular genetic methods should lead to a clear understanding of the molecular basis of electrical excitability.     

TMEM16A, a membrane protein associated with calcium-dependent chloride channel activity

Calcium-dependent chloride channels are required for normal electrolyte and fluid secretion, olfactory perception, and neuronal and smooth muscle excitability. The molecular identity of these membrane proteins is still unclear. Treatment of bronchial epithelial cells with interleukin-4 (IL-4) causes increased calcium-dependent chloride channel activity, presumably by regulating expression of the corresponding genes. We performed a global gene expression analysis to identify membrane proteins that are regulated by IL-4. Transfection of epithelial cells with specific small interfering RNA against each of these proteins shows that TMEM16A, a member of a family of putative plasma membrane proteins with unknown function, is associated with calcium-dependent chloride current, as measured with halide-sensitive fluorescent proteins, short-circuit current, and patch-clamp techniques. Our results indicate that TMEM16A is an intrinsic constituent of the calcium-dependent chloride channel. Identification of a previously unknown family of membrane proteins associated with chloride channel function will improve our understanding of chloride transport physiopathology and allow for the development of pharmacological tools useful for basic research and drug development.     

果树抗寒性研究进展

综述了国内外学者在果树抗寒性研究方面的新进展,包括细胞结构及其动态变化、组织器官类型、生理生化机制、分子生物学和抗寒途径等方面。同时,对今后果树抗寒性着重研究的领域提出展望。     

Three-dimensional structure of a recombinant gap junction membrane channel

Gap junction membrane channels mediate electrical and metabolic coupling between adjacent cells. The structure of a recombinant cardiac gap junction channel was determined by electron crystallography at resolutions of 7.5 angstroms in the membrane plane and 21 angstroms in the vertical direction. The dodecameric channel was formed by the end-to-end docking of two hexamers, each of which displayed 24 rods of density in the membrane interior, which is consistent with an alpha-helical conformation for the four transmembrane domains of each connexin subunit. The transmembrane alpha-helical rods contrasted with the double-layered appearance of the extracellular domains. Although not indicative for a particular type of secondary structure, the protein density that formed the extracellular vestibule provided a tight seal to exclude the exchange of substances with the extracellular milieu.     

分子标记在丛枝菌根研究中的应用

 作为一类具有重要生态学意义的微生物类群,丛枝菌根（Arbuscular mycorrhizal,AM）真菌在自然生态系统中的功能已经成为当前生态学研究的热点问题之一,其中,AM真菌的分类鉴定是菌根学研究的重要组成部分。鉴于经典的菌根真菌鉴定技术的局限性,本文围绕以PCR为基础的分子生物学技术,探究RAPD、RFLP、SSCP、AFLP等在AM真菌分类鉴定、亲缘关系分析、多态性测定以及群落结构组成等方面的应用及其取得的成果,并对不同分子生物学技术之间的优缺点进行对比。在此基础上,对利用分子标记技术开展AM真菌研究的前景进行展望。     

Mutations affecting TEA blockade and ion permeation in voltage-activated K+ channels

Voltage-dependent ion channels are responsible for electrical signaling in neurons and other cells. The main classes of voltage-dependent channels (sodium-, calcium-, and potassium-selective channels) have closely related molecular structures. For one member of this superfamily, the transiently voltage-activated Shaker H4 potassium channel, specific amino acid residues have now been identified that affect channel blockade by the small ion tetraethylammonium, as well as the conduction of ions through the pore. Furthermore, variation at one of these amino acid positions among naturally occurring potassium channels may account for most of their differences in sensitivity to tetraethylammonium.     

IAA分解代谢相关酶（IAAO、POD）的研究进展

 吲哚乙酸IAA参与植物体内诸多生理活动,其分解代谢相关酶吲哚乙酸氧化酶（IAAO）、过氧化物酶（POD）在IAA代谢过程中起着关键作用,二者通过调控植物体内IAA的水平来调控复杂的植物生长,该文综合总结了IAAO和POD近年来研究的相关进展,尤其是结合生物化学和分子生物学方面阐述了这两种酶在IAA代谢中的作用及其相关性。