Balanced inhibition underlies tuning and sharpens spike timing in auditory cortex

Neurons in the primary auditory cortex are tuned to the intensity and specific frequencies of sounds, but the synaptic mechanisms underlying this tuning remain uncertain. Inhibition seems to have a functional role in the formation of cortical receptive fields, because stimuli often suppress similar or neighbouring responses, and pharmacological blockade of inhibition broadens tuning curves. Here we use whole-cell recordings in vivo to disentangle the roles of excitatory and inhibitory activity in the tone-evoked responses of single neurons in the auditory cortex. The excitatory and inhibitory receptive fields cover almost exactly the same areas, in contrast to the predictions of classical lateral inhibition models. Thus, although inhibition is typically as strong as excitation, it is not necessary to establish tuning, even in the receptive field surround. However, inhibition and excitation occurred in a precise and stereotyped temporal sequence: an initial barrage of excitatory input was rapidly quenched by inhibition, truncating the spiking response within a few (1-4) milliseconds. Balanced inhibition might thus serve to increase the temporal precision and thereby reduce the randomness of cortical operation, rather than to increase noise as has been proposed previously.     

基于数学形态学预处理的神经元放电检测

神经元放电检测是对后续神经元放电波形的聚类分析、神经元放电串的统计分析等工作都非常关键的第一步。为了尽可能准确地把神经元放电从背景噪声中分离出来,该文首先应用数学形态学对原始记录数据进行预处理,然后再经过阈值处理把神经元放电检测出来。选择和放电波形在形状、持续时间和幅度上都相近的结构元素,数学形态学预处理步骤能有效地滤除原始记录中的背景噪声,突出放电信号。对神经元放电仿真数据集和实验记录的大鼠海马区神经元自发放电的检测结果显示:基于数学形态学预处理的神经元放电检测方法的准确率要高于常用的直接进行阈值处理的检测方法。     

Double-strand breaks at an initiation site for meiotic gene conversion

It has been proposed that the initiation of meiotic recombination involves either single-strand or double-strand breaks in DNA. It is difficult to distinguish between these on the basis of genetic evidence because they give rise to similar predictions. All models invoke initiation at specific sites to explain polarity, which is a gradient in gene conversion frequency from one end of a gene to the other. In the accompanying paper we describe the localization of an initiation site for gene conversion to the promoter region of the ARG4 gene of the yeast Saccharomyces cerevisiae. Here, we show that a double-strand break appears at the ARG4 recombination initiation site at the time of recombination, and that the broken DNA molecules end in long single-stranded tails.     

基于听感知特征的英语句子重音检测

为了更有效地提取英语句子重音,提出了一种基于听感知特征的方法。根据音素特点,改进段长的归一化方法;根据听感知特性,引入半音程和响度特征,并以归一化的音节最高值代替其平均值,系统正确率达到78.7%,漏检率为9.37%。在此基础上,还提出了基于掩蔽效应的突显度模型,系统正确率提高到83.4%,漏检率下降到5.72%。实验表明,突显度模型更符合人的听感知,其性能接近人工标注的一致率(约为86%)。系统还具有文本无关和说话人无关的优点。     

An initiation site for meiotic gene conversion in the yeast Saccharomyces cerevisiae

An initiation site for meiotic gene conversion has been identified in the promoter region of the ARG4 gene of Saccharomyces cerevisiae. The chromosome on which initiation occurs is the recipient of genetic information during gene conversion.     

Cell-type-specific replication initiation programs set fragility of the FRA3B fragile site

Common fragile sites have long been identified by cytogeneticists as chromosomal regions prone to breakage upon replication stress. They are increasingly recognized to be preferential targets for oncogene-induced DNA damage in pre-neoplastic lesions and hotspots for chromosomal rearrangements in various cancers. Common fragile site instability was attributed to the fact that they contain sequences prone to form secondary structures that may impair replication fork movement, possibly leading to fork collapse resulting in DNA breaks. Here we show, in contrast to this view, that the fragility of FRA3B--the most active common fragile site in human lymphocytes--does not rely on fork slowing or stalling but on a paucity of initiation events. Indeed, in lymphoblastoid cells, but not in fibroblasts, initiation events are excluded from a FRA3B core extending approximately 700 kilobases, which forces forks coming from flanking regions to cover long distances in order to complete replication. We also show that origins of the flanking regions fire in mid-S phase, leaving the site incompletely replicated upon fork slowing. Notably, FRA3B instability is specific to cells showing this particular initiation pattern. The fact that both origin setting and replication timing are highly plastic in mammalian cells explains the tissue specificity of common fragile site instability we observed. Thus, we propose that common fragile sites correspond to the latest initiation-poor regions to complete replication in a given cell type. For historical reasons, common fragile sites have been essentially mapped in lymphocytes. Therefore, common fragile site contribution to chromosomal rearrangements in tumours should be reassessed after mapping fragile sites in the cell type from which each tumour originates.     

Uncoupling of initiation site cleavage from subsequent headful cleavages in bacteriophage T1 DNA packaging

The packaging of intracellular DNA into heads is a key feature in the morphogenesis of bacteriophage particles. In many phages a performed empty head precursor, the prohead, is filled with DNA from a concatemeric substrate consisting of tandemly repeated genome lengths. The addition of outer shell proteins completes head formation. The DNA molecules released from particles of the coliphage T1 exist as three major permutations of nucleotide sequence. Such limited permutation can be explained by the modification of Streisinger's 'headful' mechanism proposed for phage P22. DNA packaging is initiated at a specific site (the pac site) on the concatemeric precursor. While this site is cleaved, subsequent cleavages (headful cleavages) are dependent only on head-filling and are not defined in terms of nucleotide sequence. Headfuls of DNA, consisting of slightly more than a genome length, are packaged in three successive cycles of head-filling to produce the permuted and terminally redundant molecules characteristic of T1 DNA. To elucidate the regulation of this process, we have studied the DNA metabolism of T1 head mutants. We describe here the properties of a mutant in gene 13.3 which is defective for headful cleavage but remains proficient in pac site cleavage. The observation in this mutant that concatemers are degraded to unit-length molecules by repeated pac site cleavage suggests a model of headful packaging in which pac site initiation and processive head-filling compete for the DNA substrate.     

蒲棒浸提液机制下黑木耳发酵方法及相关检测

通过单因素实验与正交实验,研究得到在蒲棒浸提液基质下黑木耳发酵的最适碳、氮源及其最优配方.取其发酵最佳菌龄的发酵醪液做匀浆处理,用于培养供试黑腹果蝇,进行果蝇寿命实验,观察记录其对果蝇生存寿命的影响.结果表明:最优发酵配方各组分质量分数分别为葡萄糖3%,玉米粉3%,豆饼粉2%,酵母膏0.5%,磷酸二氢钾0.1%,硫酸镁0.1%;在发酵至120 h时,鲜菌丝质量达到最大,为32.57 g.在果蝇基础培养基内添加体积分数为30%的发酵醪液匀浆时,果蝇的半数死亡期延长率、平均延寿率和最高延寿率最大,且均与对照组有显著性差异(P<0.05).     

脑弥散性轴索损伤的诊断与治疗

目的 探讨脑弥散性轴索损伤(DAI)的诊断与治疗。方法 回顾36例DAI患者诊治经过．结果 按Glasgow outcomescale治疗，良好8例，中残10例，重残2例，植物生存2例，死亡14例。结论 CT及MRI是诊断DAI的重要手段。早期诊断及治疗是提高DAI病人治愈率，降低死亡率及致残率的关键。     

离子-原子碰撞中的符合测量技术

利用离子源产生的C、O离子与Ar原子碰撞,测量了散射离子谱和反冲离子谱,并利用符合测量获取了双电荷态分布的符合谱。根据实验参数进行了符合效率计算。该实验方法可用于微量气体元素甚至同位素的绝对含量分析,较单独的飞行时间谱更加可靠。     

Recognition and initiation site for four late promoters of phage T7 is a 22-base pair DNA sequence

T7 late promoters have a 22-base pair sequence in common. The 22 base pairs are necessary and sufficient for recognition and initiation by T7 RNA polymerase.     

Research on community detection algorithm based on site topic similarity and topology

Considering the deviation in content of community detection resulting from the low accuracy of resource relevance,an algorithm based on the topology of sites and the similarity between their topics is proposed. With topic content factors fully considered,this algorithm can search for topically similar site clusters on the premise of inter-site topology. The experimental results show that the algorithm can generate a more accurate result of detection in the real network.     

Reconstruction of the most recent common ancestor sequences of SARS-Cov S gene and detection of adaptive evolution in the spike protein

The genome organization and expression strategy of severe acute respiratory syndrome coronavirus (SARS-CoV) have been described extensively. As a structural glycoprotein on the virion surface, the spike protein is responsible for binding to host cellular receptors and for the fusion between the viral envelope and the cellular membrane. It also induces neutralizing antibodies in     

高密度电法在WLQC工地废弃水井探测中的应用

在WLQC工地建设工程中,利用高密度电法对工地废弃水井进行探测,运用合理观测方式,结合高密度反演软件处理解释,查明了废弃水井的空间范围及其对施工的影响,取得了良好的地质效果.通过探测及时排除了给施工单位人员、设备带来的安全隐患并且为建设单位的设计提供了依据.实验结果表明在遇到水泥预制,场地勘探空间受到极大限制等施工工地的问题的勘测工作中,高密度电法具有成本低、效率高、效果好、显示直观等特点,不失为一种值得大力推广的好方法.     

阈值光电子-光离子符合速度成像技术的初步应用

基于同步辐射的闲值光电子-光离子符合速度成像技术采用双速度聚焦电场同时控制电子和离子的飞行轨迹,提高了收集效率和能量分辨率.应用该技术开展了一些原子和分子的实验研究,分别测量了相应的阈值光电子谱、阈值光电子-光离子符合质谱、阈值光电子-光离子符合光谱和阈值光电子-光离子符合速度成像,展现了该技术在离子结构分析、混合物成分辨别和具有态选择的离子解离动力学等方面的初步应用.     

SWI对脑创伤性轴索损伤的诊断价值

目的:探讨磁敏感加权成像(SWI)对弥漫性轴索损伤(DAI)的诊断价值.方法:对40例临床诊断为DAI病例常规T1WI,T2WI液体衰减反转恢复(FLAIR)序列和磁共振弥散加权(DWI)及磁敏感加权(SWI)扫描.结果:SWI可清楚显示31例DAI的颅内异常小出血灶,为点状、条索状、类圆形或串珠状的低信号影,检出率77.5%,分别同常规T1WI,T2WI序列检出率15%,32.5%(χ2=31.43,P=0.01,χ2=16.36,P=0.01),同FLAIR序列检出率50%,DWI序列57.5%(χ2=6.54,P0.05,χ2=3.65,P0.05).结论:SWI能非常敏感地检出外伤后弥漫性轴索损伤患者的脑内小出血灶,对弥漫性轴索损伤有很高的诊断价值.     

Axonal transport of vasoactive intestinal peptide in sciatic nerve.

Dense plexuses of neurones containing immunoreactive vasoactive intestinal peptide (VIP) have been found in discrete areas of the central nervous system and in peripheral organs, including the gastrointestinal tract, pancreas and urogenital system. In many of these locations VIP is concentrated in nerve endings, where it can be released by high K+ concentrations in a Ca2+-dependent manner. VIP release may also be provoked by electrical stimulation of nerves, for example the vagus. VIP thus shows some of the features of neurotransmitter or neuromodulator substances. The presence of immunoreactive VIP in the fine terminal varicosities as well as in the cell bodies of neurones suggests that it might be transported from the perikaryon, where it is presumably formed, to the nerve endings, through the axonal transport system. Such transport would be in keeping with a role for the peptide as a neurohumor or neurohormone. We report here that VIP accumulates in constricted rat sciatic nerves in a manner suggesting fast, anterograde axonal flow.