Axonal proteins of presynaptic neurons during synaptogenesis

Changes occur in the synthesis and axonal transport of neuronal proteins in dorsal-root ganglia axons as a result of contact with cells from the spinal cord during synapse formation. Dorsal-root ganglia cells were cultured in a compartmental cel culture system that allows separate access to neuronal cell bodies and their axons. When cells from the ventral spinal cord were cultured with the dorsal-root ganglia axons, synapses were established within a few days. Metabolic labeling and two-dimensional electrophoresis revealed that four of more than 300 axonal proteins had changed in their expression by the time synapses were established. The highly selective nature of these changes suggests that the proteins involved may be important in the processes of axon growth and synapse formation and their regulation by the regional environment.     

Emerging roles of presynaptic proteins in Ca++-triggered exocytosis

The twinning of techniques from biophysics and molecular biology has led to remarkable progress in understanding the molecular mechanisms of synaptic transmission. Here we review the current picture of Ca++-triggered exocytosis, which has emerged from studies of a simple cellular model, the adrenal chromaffin cell. We discuss the molecular players that have been assigned a specific role in a particular step of this process and give a brief outlook on what these insights might tell us about mechanisms of short-term plasticity at classical synapses.     

Rapid 20th-century increase in coastal upwelling off northwest Africa

Near-shore waters along the northwest African margin are characterized by coastal upwelling and represent one of the world's major upwelling regions. Sea surface temperature (SST) records from Moroccan sediment cores, extending back 2500 years, reveal anomalous and unprecedented cooling during the 20th century, which is consistent with increased upwelling. Upwelling-driven SSTs also vary out of phase with millennial-scale changes in Northern Hemisphere temperature anomalies (NHTAs) and show relatively warm conditions during the Little Ice Age and relatively cool conditions during the Medieval Warm Period. Together, these results suggest that coastal upwelling varies with NHTAs and that upwelling off northwest Africa may continue to intensify as global warming and atmospheric CO2 levels increase.     

Rapid axonal transport of sulfated mucopolysaccharide proteins

When sulfur-35-labeled sodium sulfate is injected intraocularly in the goldfish, labeled sulfated mucopolysaccharides rapidly appear in the contra-lateral optic tectum of the brain, demonstrating the axonal flow of sulfated mucopolysaccharides. The transport rate is the same as that observed for proteins labeled after intraocular injection of tritiated proline. Treatment of the sulfur-35-labeled material with precipitants and enzymes reveals the presence of substances with properties similar to those of heparan sulfate (the major component) and chondroitin sulfate. Dermatan sulfate was not detected.     

聚乙二醇修饰蛋白的快速分离与纯化

【目的】建立聚乙二醇修饰蛋白的快速分离纯化方法。【方法】以4种聚乙二醇化药用蛋白为研究对象,采用阳离子交换树脂进行纯化。纯化条件:Hiprep 16/10 CM Sepharose FF(1 mL)预装柱;流动相:A液为20mmol/L pH4.0的醋酸缓冲液;B液为A液中加入1 mol/L NaCl;B液以0~100%离子强度线性梯度洗脱100 min,流速0.2 mL/min,波长280 nm检测,收集各洗脱峰。【结果】一步纯化可将单点修饰产物与聚乙二醇、多点修饰产物以及未修饰蛋白分离开来,单点修饰产物经SDS-PAGE检测呈单一条带,经质谱检测其相对分子质量与预期相符。【结论】所建立的纯化方法可快速分离纯化聚乙二醇修饰蛋白。     

Rapid increase of phenylethanolamine N-methyltransferase by environmental stress in an inbred mouse strains

The activity of-phenylethanolamine N-methyltransferase in mice of the C57Bl/Ka strain was determined after a 4 degrees C stress. The enzyme activity increased 1.2-fold at the end of 3 hours and by 1.4-fold by the end of 6 hours of the stress. The results are in contrast to those from other species with intact animals in which the enzyme changes only after several days of chronic stress. Cycloheximide prevents the rise in enzyme activity, suggesting the increase may be due to protein synthesis. The increase may provide a model system for studying regulation of catecholamine biosynthetic enzymes.     

基于个案的区域农业集群成长思考

在高新技术产业、制造业等领域涌现了大量成功的产业集群范例。笔者分析认为，现代农业不仅可以产生集群，而且比传统形式的农业更有竞争力。但农业集群的形成及其竞争优势的获得是一个长期的重复博弈过程，具有一定的内生性质，政府不能刻意创造农业集群。农业集群以诱致性形成为主，成长路径因诱因不同而各异。以江苏部分集群为个案，重点考察了农业集群成长的三种路径，并提出相应的政府战略选择。     

Increase in salicylic Acid at the onset of systemic acquired resistance in cucumber

In an effort to identify the signal compound that mediates systemic acquired resistance (SAR), changes in the content of phloem sap were monitored in cucumber plants inoculated with either tobacco necrosis virus or the fungal pathogen Colletotrichum lagenarium. The concentration of a fluorescent metabolite was observed to increase transiently after inoculation, with a peak reached before SAR was detected. The compound was purified and identified by gas chromatography-mass spectrometry as salicylic acid, a known exogenous inducer of resistance. The data suggest that salicylic acid could function as the endogenous signal in the transmission of SAR in cucumber.     

Tenfold population increase in Western Europe at the Neandertal-to-modern human transition

European Neandertals were replaced by modern human populations from Africa ~40,000 years ago. Archaeological evidence from the best-documented region of Europe shows that during this replacement human populations increased by one order of magnitude, suggesting that numerical supremacy alone may have been a critical factor in facilitating this replacement.     

利用SDS-PAGE电泳快速检测茎用芥菜细胞质雄性不育系特异表达蛋白(英文)

本研究利用SDS-PAGE电泳直接检测到茎用芥菜细胞质雄性不育系花器中存在两种特异表达白,分子量约分别为14.4 kD和43.0 kD,其中14.4 kD蛋白在不育系花器中存在明显的过量表达现象;而不育系和保持系营养生长和生殖生长期叶片和根中蛋白电泳谱带未发现差异,特异蛋白的表达有很强的器官特异性.我们推测此两种特异蛋白的产生可能与茎用芥菜细胞质胞质雄性不育的表达有关.     

Anomalous increase in carbon capacitance at pore sizes less than 1 nanometer

Carbon supercapacitors, which are energy storage devices that use ion adsorption on the surface of highly porous materials to store charge, have numerous advantages over other power-source technologies, but could realize further gains if their electrodes were properly optimized. Studying the effect of the pore size on capacitance could potentially improve performance by maximizing the electrode surface area accessible to electrolyte ions, but until recently, no studies had addressed the lower size limit of accessible pores. Using carbide-derived carbon, we generated pores with average sizes from 0.6 to 2.25 nanometer and studied double-layer capacitance in an organic electrolyte. The results challenge the long-held axiom that pores smaller than the size of solvated electrolyte ions are incapable of contributing to charge storage.     

Activity-dependent enhancement of presynaptic inhibition in Aplysia sensory neurons

Tail shock produces transient presynaptic inhibition and longer lasting presynaptic facilitation of the siphon sensory neurons in Aplysia. The facilitation undergoes activity-dependent enhancement that is thought to contribute to classical conditioning of the gill- and siphon-withdrawal reflex. Inhibition of the sensory neurons has now also been shown to undergo activity-dependent enhancement when action potential activity in the sensory neurons is paired with inhibitory transmitter. This effect appears to involve an amplification of the same cellular mechanisms that are involved in normal presynaptic inhibition. These results suggest that activity-dependent enhancement may be a general type of associative cellular mechanism.     

Rapid formation of sulfuric acid particles at near-atmospheric conditions

We investigated the formation of new particles in a laboratory study, starting from H2SO4 produced in situ through the reaction of OH radicals with SO2. Newly formed particles were observed for H2SO4 concentrations above 7 x 10(6) per cubic centimeter. At 293 kelvin, a rough estimate yielded a nucleation rate of 0.3 to 0.4 particles per cubic centimeter per second for approximately 10(7) particles per cubic centimeter of H2SO4 (particle size >/= 3 nanometers). These findings are in agreement with observations from the atmosphere. The results demonstrate that under laboratory conditions similar to the atmosphere, particle formation occurs at atmospheric H2SO4 concentration levels.     

Neuronal calcium sensor 1 and activity-dependent facilitation of P/Q-type calcium currents at presynaptic nerve terminals

P/Q-type presynaptic calcium currents (IpCa) undergo activity-dependent facilitation during repetitive activation at the calyx of the Held synapse. We investigated whether neuronal calcium sensor 1 (NCS-1) may underlie this phenomenon. Direct loading of NCS-1 into the nerve terminal mimicked activity-dependent IpCa facilitation by accelerating the activation time of IpCa in a Ca2+-dependent manner. A presynaptically loaded carboxyl-terminal peptide of NCS-1 abolished IpCa facilitation. These results suggest that residual Ca2+ activates endogenous NCS-1, thereby facilitating IpCa. Because both P/Q-type Ca2+ channels and NCS-1 are widely expressed in mammalian nerve terminals, NCS-1 may contribute to the activity-dependent synaptic facilitation at many synapses.     

Membrane-associated particles: increase at sites of pinocytosis demonstrated by freeze-etching

An increased number of membrane-associated particles has been demonstrated by freeze-etching in areas of pinocytosis in the intestinal smooth muscle cell. A peculiar distribution of the particles is described, which might be closely related to the formation of pinocytotic vesicles (caveolae).     

Enzymatic solubilization of insoluble proteins at neutral pH

Insoluble epidermal proteins (possibly keratin), previously considered inert to enzyme action, were solubilized by either trypsin or chymotrypsin.Cleavage of the disulfide bonds prior to enzymatic action is not necessary.In addition, the enzymatic action on intact epidermis is not influenced by the presence or absence of endogenous lipids, soluble proteins, peptides, or amino acids. Solubilization of epidermal protein by chymotrypsin is inhibited by the supernatant solution of the homogenized epidermis.     

Indole-2-carboxylic acid: a competitive antagonist of potentiation by glycine at the NMDA receptor

The N-methyl-D-aspartate (NMDA) class of excitatory amino acid receptors regulates the strength and stability of excitatory synapses and appears to play a major role in excitotoxic neuronal death associated with stroke and epilepsy. The conductance increase gated by NMDA is potentiated by the amino acid glycine, which acts at an allosteric site tightly coupled to the NMDA receptor. Indole-2-carboxylic acid (I2CA) specifically and competitively inhibits the potentiation by glycine of NMDA-gated current. In solutions containing low levels of glycine, I2CA completely blocks the response to NMDA, suggesting that NMDA alone is not sufficient for channel activation. I2CA will be useful for defining the interaction of glycine with NMDA receptors and for determining the in vivo role of glycine in excitotoxicity and synapse stabilization.     

植物胚胎发育时期特异蛋白的研究进展

综述了近年来植物胚胎发育时期特异蛋白的研究进展,包括胚胎特异蛋白的分离、鉴定和相关基因的克隆、表达及调控的研究现状,并提出了该领域今后的发展方向.     

Calcium rises abruptly and briefly throughout the cell at the onset of anaphase

Continuous measurement and imaging of the intracellular free calcium ion concentration ([Ca2+]i) of mitotic and interphase PtK1 cells was accomplished with the new fluorescent Ca2+ indicator fura-2. No statistically significant difference between basal [Ca2+]i of interphase and mitotic cells was detected. However, mitotic cells showed a rapid elevation of [Ca2+]i from basal levels of 130 nM to 500 to 800 nM at the metaphase-anaphase transition. The [Ca2+]i transient was brief, lasting approximately 20 seconds and the elevated [Ca2+]i appeared uniformly distributed over the entire spindle and central region of the cell. The close temporal association of the [Ca2+]i transient with the onset of anaphase suggests that calcium may have a signaling role in this event.