Developmental and activity-dependent regulation of kainate receptors at thalamocortical synapses.

Most of the fast excitatory synaptic transmission in the mammalian brain is mediated by ionotrophic glutamate receptors, of which there are three subtypes: AMPA (alpha-amino-3-hydroxyl-5-methyl-4-isoxazolepropionate), NMDA (N-methyl-D-aspartate) and kainate. Although kainate-receptor subunits (GluR5-7, KA1 and 2) are widely expressed in the mammalian central nervous system, little is known about their function. The development of pharmacological agents that distinguish between AMPA and kainate receptors has now allowed the functions of kainate receptors to be investigated. The modulation of synaptic transmission by kainate receptors and their synaptic activation in a variety of brain regions have been reported. The expression of kainate receptor subunits is developmentally regulated but their role in plasticity and development is unknown. Here we show that developing thalamocortical synapses express postsynaptic kainate receptors as well as AMPA receptors; however, the two receptor subtypes do not colocalize. During the critical period for experience-dependent plasticity, the kainate-receptor contribution to transmission decreases; a similar decrease occurs when long-term potentiation is induced in vitro. This indicates that during development there is activity-dependent regulation of the expression of kainate receptors at thalamocortical synapses.     

Possible regulatory function of acetylcholine receptor in maintenance of retinotectal synapses.

alpha-Neurotoxins bind to cholinergic receptor, block transmission, and induce sprouting of retinal terminals in the toad tectum. New connections retain an orderliness that suggests a selective affinity between presynaptic terminals. The results suggest that postsynaptic cells exert a control, associated with receptors, on the growth of presynaptic terminals and on the maintenance of their synaptic connections.     

CaMKII regulates the density of central glutamatergic synapses in vivo

Synaptic connections undergo a dynamic process of stabilization or elimination during development, and this process is thought to be critical in memory and learning and in establishing the specificity of synaptic connections. The type II calcium- and calmodulin-dependent protein kinase (CaMKII) has been proposed to be pivotal in regulating synaptic strength and in maturation of synapses during development. Here we describe how CaMKII regulates the formation of central glutamatergic synapses in Caenorhabditis elegans. During larval development, the density of ventral nerve cord synapses containing the GLR-1 glutamate receptor is held constant despite marked changes in neurite length. The coupling of synapse number to neurite length requires both CaMKII and voltage-gated calcium channels. CaMKII regulates GLR-1 by at least two distinct mechanisms: regulating transport of GLR-1 from cell bodies to neurites; and regulating the addition or maintenance of GLR-1 to postsynaptic elements.     

感官动词的概念框架分析

从神经认知语言学的角度,以程琪龙教授提出的小句概念框架为基础,对英文中的感官动词进行分析,旨在例证概念框架比语义结构对动词更具有解释力,说明语义上有差别的句式在概念框架层面上可达到一致性。     

Transglutaminase modifies the carboxy-terminal intracellular region of HLA-A and -B antigens

The HLA-A and -B antigens, encoded in the major histocompatibility complex, are transmembrane proteins whose carboxy termini project inwards from the cell membrane. The intracellular region of the HLA-B7 antigen is known to include two glutamine residues. We have used guinea pig transglutaminase to show that in vitro the enzyme couples amines specifically to glutamine residues in the carboxy-terminal region of the HLA-B7 and -A2 antigens. The specificity of this reaction has an immediate practical significance, but may also have a wider biological interest.     

Elimination of action potentials blocks the structural development of retinogeniculate synapses

Although the influence of electrical activity on neural development has been studied extensively, experiments have only recently focused on the role of activity in the development of the mammalian central nervous system (CNS). Using tetrodotoxin (TTX) to abolish sodium-mediated action potentials, studies on the visual system show that impulse activity is essential both for the normal development of neuronal size and responsivity in the lateral geniculate nucleus (LGN), and for the eye-specific segregation of geniculo-cortical axons. There have been no anatomical studies to investigate the influence of action potentials on CNS synaptic development. We report here the first direct evidence that elimination of action potentials in the mammalian CNS blocks the growth of developing axon terminals and the formation of normal adult synaptic patterns. Our results show that when TTX is used to eliminate retinal ganglion-cell action potentials in the cat from birth to 8 weeks, the connections made by ganglion cell axons with LGN neurones, retinogeniculate synapses, remain almost identical morphologically to those in the newborn kitten.     

对男子十项全能运动员短期训练的研究

我校某十项全能运动员经过6个多月的短期训练,总分成绩从4986分提高到5689分,获得江苏省大学生运动会田径比赛十项全能第二名,根据该运动员训练前后的成绩,分析安排训练与准备比赛的思路与方法,探讨了高校十项全能新手短期训练科学化的问题,旨在提高高校十项全能运动水平和训练效益。     

影响硬糖感官品质的关键因素

主要研究了影响硬糖感官品质的关键因素．分析果葡糖浆、柠檬酸的添加量以及熬制温度、熬制时间对硬糖品质的影响,结果表明：对硬糖感官品质影响程度由大到小依次为：熬制温度、熬制时间、果葡糖浆添加量、柠檬酸的添加量．随着熬制温度的增加,硬度呈增大趋势,脆性先增大后趋于平稳,感官评价分值先增大后减小;随着熬制时间的增加,硬度和脆性都呈增大趋势,感官评价分值呈下降趋势;随着果葡糖浆添加量的增大,硬度及脆性都呈下降趋势,感官评价结果先增大后减小;随着柠檬酸添加量的增大,硬度、脆性和感官评价分值都呈先增大后减小的趋势,并且前两者变化趋势相同．熬制温度为155℃、熬制时间为5min、果葡糖浆和柠檬酸的添加量分别为10％和0．50％时,硬糖的感官品质较好．     

纺织品感官评估的进展与展望

在纺织工业生产中，对纺织品质量进行评估是非常重要的环节，由于传统的感官评估和客观评估存在自身的缺陷在实际应用中受到限制。当前的研究方法是将感官评估与客观评估结合起来。因为评估得更加有效、合理，现在已成为各个行业研究的热点。为了感官评估更好地应用，本文对以往的研究成果作了系统全面的回顾与总结。同时指出了其进一步研究的方向。     

A network of fast-spiking cells in the neocortex connected by electrical synapses

Encoding of information in the cortex is thought to depend on synchronous firing of cortical neurons. Inhibitory neurons are known to be critical in the coordination of cortical activity, but how interaction among inhibitory cells promotes synchrony is not well understood. To address this issue directly, we have recorded simultaneously from pairs of fast-spiking (FS) cells, a type of gamma-aminobutyric acid (GABA)-containing neocortical interneuron. Here we report a high occurrence of electrical coupling among FS cells. Electrical synapses were not found among pyramidal neurons or between FS cells and other cortical cells. Some FS cells were interconnected by both electrical and GABAergic synapses. We show that communication through electrical synapses allows excitatory signalling among inhibitory cells and promotes their synchronous spiking. These results indicate that electrical synapses establish a network of fast-spiking cells in the neocortex which may play a key role in coordinating cortical activity.