冬小麦花药愈伤组织无性系穗数变异的研究

从Ｈ１代花药单倍体试管苗（９０－２４３１）基部，取未分化绿苗的胚性愈伤组织建立的体细胞无性系，获得４丛Ｒ１代结实株系。从田间Ｒ２代的观察中发现，Ｒ１代的４株后代中繁衍的８６个单株发生了变异，经过这株变异的Ｒ２Ｒ３代的穗数观察发现：（１）Ｒ２和Ｒ３代单株穗数变异范围大，穗数都明显增多，并且有超亲现象；（２）Ｒ２和Ｒ３代的单株穗数呈显著正相关；（３）穗系间的变异大于穗系内的变异；（４）Ｒ３代有２９％的穗系已稳定。     

AGP转基因粳稻产量性状在低世代中的遗传与变异

云南粳稻合系３８、合系４２经ＡＧＰ基因导入后,株高,有效穗数,实粒数,千粒重等产量性状的群体变异频率在Ｔ１和Ｔ２代中显著增高,由于水稻自花授粉的特性,导入目的基因的两条同源染色体配对的频率也较高,因此在代世代中已经出现了综合性状较好的株系。     

不同产量水平玉米的性状构成分析

以近3年来参加重庆市玉米预备试验的233个品种（组合）为材料，根据其该年与对照农大108的产量增幅，划分3种类型，并比较不同类型品种（组合）不同年份的穗粒、植株性状。同时还对233个品种（组合）的产量与性状进行了相关分析与通径分析。结果表明：高产类型品种（组合）表现为高秆、长穗、深粒；性状与产量相关紧密程度依次为株高、穗位高、穗长、行粒数、千粒雨、穗行数、出籽率和秃尖长，其中行粒数和下粒霞以直接作用为主，而株高、穗位高、穗长以间接作用为主。     

科尔沁沙地冰草居群形态多样性研究

应用常规统计学方法，对科尔沁沙地冰草5个居群共计100个单株的5个形态学形状(穗长、穗宽、穗轴第一节间长、小穗小花数)进行了分析，各居群均在穗轴第一间节长这一性状表现出最大变异(CV=32．00％)，在穗长上表现出最小变异(CV=18．07％)．采用Shanno-Weaver信息指数，科尔沁沙地冰草居群多样性指数为1．5545，显示了较高的遗传多样性。     

粳稻品系数量性状相关遗传力的研究

对牡丹江农科所10个决选粳稻品系和6个数量性状进行相关遗传力的分析，在选择强度相同时，对单株产量直接选择的效率比通过其他性状间接选择效率高，单株产量与穗长、株高、单株穗数、千粒重的相关遗传贡献率均大于70％，说明表型相关变异中大部分是由遗传成分引起的，环境造成的相关变异很小，千粒单株穗数对单株产量有较大的直接作用。     

普通小麦与高冰草不对称体细胞杂种F_2代 Ⅰ表型与性状分析

普通小麦（ＴｒｉｔｉｃｕｍａｅｓｔｉｖｕｍＬ．）济南１７７原生质体和经紫外线照射的高冰草（Ａｇｒｏｐｙｒｏｎｅｌｏｎｇａｔｕｍ）原生质体用ＰＥＧ法诱导融合，形成杂种植株，但未能正常结实．杂种植株经子房诱导产生可育Ｆ０代；将Ｆ０代产生的４粒种子播种后产生Ｆ１代植株，对由其产生的Ｆ２代４个株系进行田间观察和室内考种．分析表明，Ｆ２代植株的表现型及产量性状均明显优于亲本小麦．田间穗行、株系表型稳定，具有抗寒、茎杆硬、抗倒伏等优良性状．在分蘖数、单株粒重及千粒重等产量性状上亦有明显优势，此研究为培育体细胞杂种优良小麦品系奠定了基础．     

导入野生大豆DNA小麦后代的农艺性状研究

用花粉管通道法将野生大豆总DNA导入小麦，获得了转基因小麦，其后代的农艺性状有较大的变化。田间实验分析了变异系小麦植株与对照植株在叶片的光合速率、蒸腾速率、叶面积及株高、穗粒、穗重等性状上的差异。t检验结果显示，变异系小麦在叶面性状及产量性状上的差异是显著的，外源DNA的导入改善了植物的农艺性状，并在后代中表达，为选育高产、优质的新小麦品种提供了依据。     

玉米雄穗性状的配合车及相关研究

以南２１－３等７个玉米自交系为亲本,按照双列设计组配一套不包括反交的组合。对雄穗主轴长,雄穗分枝数,雄穗总分枝长进行配合力分析及相关研究。结果表明,３个雄穗性状的ＧＣＡ,ＳＣＡ效应及变异程度均存在显著差异;３个雄穗性状的ＧＣＡ,ＳＣＡ在其性表现型值存在显著或极显著正相关。除主轴长与分枝数的ＧＣＡ外,３个雄穗性状的ＧＣＡ和ＳＣ之间具有极显著的相关关系。     

普通小麦与高冰草不对称体细胞杂种F2代：Ⅰ表型与性状 …

普通小麦济南１７７原生质体和经紫外线照射的高冰草原生质体用ＰＥＧ法诱导融合,形成杂种植株,但未能正常结实。杂种植株经子房诱导产生可育Ｆ０代;将Ｆ０代产生的４粒种子播种后产生Ｆ１代植株,对由其产生的Ｆ２代４个株系进行田间观察和室内考种。分析表明,Ｆ２代植株的表现型及产量性状均明显优于亲本小麦。田间穗行,株系表型稳定,具有抗寒、茎杆硬、抗倒伏等优良性状。在分蘖数、单株粒重衣千粒重等产量性状上亦有明显优     

激光—核辐射诱变小麦茎杆性状的遗传变异研究

本试验采用N_2激光和He-Ne激光辐照“绵阳21号”等四个小麦材料的干种子,采用随机区组设计,重复三次,利用生物统计和数量遗传学的方法,对L_1和L_2两代的株高、穗颈长等11个茎杆性状的遗传变异进行研究。结果表明:辐射材料不同,诱变后代的变异差异明显;激光种类不同,后代变异差异不大;株高、穗颈长的遗传力较高,早代单株选择的效果较好。     

铝胁迫对车前生殖特性的影响

低浓度的铝胁迫处理对车前（Plantago asiatica L.）的开花物候没有显著影响,而高浓度处理下,不仅车前的高峰期当日平均穗长及其花数、终花当日平均穗数及其穗长显著下降,且始花目推迟,花期持续时间缩短;还导致车前平均抽穗数、穗长和开花数显著减少。但对可结实车前的种子千粒重无显著影响。     

小麦新种质241主要特异性状的遗传性

为了探求小麦新种质241巨穗、粒大、结实率高等优良性状的遗传机理,应用单体分析和双端体分析方法对241材料进行遗传学研究。结果表明,小麦种质材料241的3A、5A、2B、1D和6D染色体上具有控制穗长的基因,其中2B染色体上的基因表现为强效,3A、5A、1D和6D染色体上的基因表现为弱效。控制穗长的基因定位在3AL、5AL、1DL和6DL染色体臂上,其中6DL染色体臂上可能具有控制241穗长的1个新基因。     

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。     

Distribution and three-dimensional structure of AIDS virus envelope spikes

Envelope glycoprotein (Env) spikes on AIDS retroviruses initiate infection of host cells and are therefore targets for vaccine development. Though crystal structures for partial Env subunits are known, the structure and distribution of native Env spikes on virions is obscure. We applied cryoelectron microscopy tomography to define ultrastructural details of spikes. Virions of wild-type human immunodeficiency virus 1 (HIV-1) and a mutant simian immunodeficiency virus (SIV) had approximately 14 and approximately 73 spikes per particle, respectively, with some clustering of HIV-1 spikes. Three-dimensional averaging showed that the surface glycoprotein (gp120) 'head' of each subunit of the trimeric SIV spike contains a primary mass, with two secondary lobes. The transmembrane glycoprotein 'stalk' of each trimer is composed of three independent legs that project obliquely from the trimer head, tripod-like. Reconciling available atomic structures with the three-dimensional whole spike density map yields insights into the orientation of Env spike structural elements and possible structural bases of their functions.     

Spike-timing-dependent synaptic modification induced by natural spike trains

The strength of the connection between two neurons can be modified by activity, in a way that depends on the timing of neuronal firing on either side of the synapse. This spike-timing-dependent plasticity (STDP) has been studied by systematically varying the intervals between pre- and postsynaptic spikes. Here we studied how STDP operates in the context of more natural spike trains. We found that in visual cortical slices the contribution of each pre-/postsynaptic spike pair to synaptic modification depends not only on the interval between the pair, but also on the timing of preceding spikes. The efficacy of each spike in synaptic modification was suppressed by the preceding spike in the same neuron, occurring within several tens of milliseconds. The direction and magnitude of synaptic modifications induced by spike patterns recorded in vivo in response to natural visual stimuli were well predicted by incorporating the suppressive inter-spike interaction within each neuron. Thus, activity-induced synaptic modification depends not only on the relative spike timing between the neurons, but also on the spiking pattern within each neuron. For natural spike trains, the timing of the first spike in each burst is dominant in synaptic modification.     

Axonal site of spike initiation enhances auditory coincidence detection

Neurons initiate spikes in the axon initial segment or at the first node in the axon. However, it is not yet understood how the site of spike initiation affects neuronal activity and function. In nucleus laminaris of birds, neurons behave as coincidence detectors for sound source localization and encode interaural time differences (ITDs) separately at each characteristic frequency (CF). Here we show, in nucleus laminaris of the chick, that the site of spike initiation in the axon is arranged at a distance from the soma, so as to achieve the highest ITD sensitivity at each CF. Na+ channels were not found in the soma of high-CF (2.5-3.3 kHz) and middle-CF (1.0-2.5 kHz) neurons but were clustered within a short segment of the axon separated by 20-50 microm from the soma; in low-CF (0.4-1.0 kHz) neurons they were clustered in a longer stretch of the axon closer to the soma. Thus, neurons initiate spikes at a more remote site as the CF of neurons increases. Consequently, the somatic amplitudes of both orthodromic and antidromic spikes were small in high-CF and middle-CF neurons and were large in low-CF neurons. Computer simulation showed that the geometry of the initiation site was optimized to reduce the threshold of spike generation and to increase the ITD sensitivity at each CF. Especially in high-CF neurons, a distant localization of the spike initiation site improved the ITD sensitivity because of electrical isolation of the initiation site from the soma and dendrites, and because of reduction of Na+-channel inactivation by attenuating the temporal summation of synaptic potentials through the low-pass filtering along the axon.     

重叠穗大麦的选育

重叠穗大麦系辐射突变选育而成。它是一种穗部性状的突变类型。小穗重叠着生在穗轴上。它的选育成功,不仅增加了作物的类型,而且丰富了大麦的基因库。     

基于人工神经网络的低信噪比神经元锋电位分类

基于人工神经网络和模板匹配,提出了对低信噪比神经元信号分类的方法.首先对待分类信号进行阈值检测,获得尖峰信号,对这些尖峰信号进行主成分分析,再选取主成分进行聚类,根据聚类结果,取对应的尖峰信号作为人工神经网络的训练样本.网络测试和结合模板匹配识别叠加信号的仿真结果表明了该方法的优越性.     

Spike train dynamics predicts theta-related phase precession in hippocampal pyramidal cells

According to the temporal coding hypothesis, neurons encode information by the exact timing of spikes. An example of temporal coding is the hippocampal phase precession phenomenon, in which the timing of pyramidal cell spikes relative to the theta rhythm shows a unidirectional forward precession during spatial behaviour. Here we show that phase precession occurs in both spatial and non-spatial behaviours. We found that spike phase correlated with instantaneous discharge rate, and processed unidirectionally at high rates, regardless of behaviour. The spatial phase precession phenomenon is therefore a manifestation of a more fundamental principle governing the timing of pyramidal cell discharge. We suggest that intrinsic properties of pyramidal cells have a key role in determining spike times, and that the interplay between the magnitude of dendritic excitation and rhythmic inhibition of the somatic region is responsible for the phase assignment of spikes.     

Localization of VP4 neutralization sites in rotavirus by three-dimensional cryo-electron microscopy

Three-dimensional structures of several spherical viruses have been determined by electron microscopy and X-ray crystallography. We report here the first three-dimensional structure of the complex between an intact virus and Fab fragments of a neutralizing monoclonal antibody. The antibody is against VP4, one of the two outer capsid proteins of rotaviruses. These large icosahedral viruses cause gastroenteritis in children and young animals and account for over a million human deaths annually. VP4 in these viruses has been implicated in several important functions such as cell penetration, haemagglutination, neutralization and virulence. Here we demonstrate that the surface spikes on rotavirus particles are made up of VP4. Antigenic sites are located near the distal ends of the spikes and two Fab fragments bind to each of the sixty spikes. The mass of the spike indicates that it is a dimer of VP4. The bilobed structure at the distal end of the spike may be involved in both the attachment to the cell and in viral penetration. A novel feature in the virus-Fab complex is the structural difference between the two chemically equivalent Fab fragments on each spike, which could be indicative of variations in the Fab elbow angles.