Transient cells of the developing mammalian telencephalon are peptide-immunoreactive neurons

In the development of the mammalian telencephalon, the genesis of neurons destined for the various layers of the cerebral cortex is preceded by the generation of a population of cells that comes to reside in the subplate and marginal zones (see ref. 2 for nomenclature). In the cat, these cells are present in large numbers during development, when their location is correlated with the arrival and accumulation of ingrowing axonal systems and with synapses. However, as the brain matures, the cells disappear and the white matter and layer 1 of the adult emerge. Their disappearance occurs in concert with the invasion of the cortical plate by the axonal systems and with the elimination of the synapses from the subplate. Here we report that the subplate cells have properties typical of mature neurons. They have the ultrastructural appearance of neurons and receive synaptic contacts. They also have long projections and are immunoreactive for MAP2 (microtubule associated protein 2). Further, subpopulations are immunoreactive for one of several neuropeptides. These observations suggest that during the fetal and early postnatal development of the mammalian telencephalon the subplate cells function as neurons in synaptic circuitry that disappears by adulthood.     

Amygdala intercalated neurons are required for expression of fear extinction

Congruent findings from studies of fear learning in animals and humans indicate that research on the circuits mediating fear constitutes our best hope of understanding human anxiety disorders. In mammals, repeated presentations of a conditioned stimulus that was previously paired to a noxious stimulus leads to the gradual disappearance of conditioned fear responses. Although much evidence suggests that this extinction process depends on plastic events in the amygdala, the underlying mechanisms remain unclear. Intercalated (ITC) amygdala neurons constitute probable mediators of extinction because they receive information about the conditioned stimulus from the basolateral amygdala (BLA), and contribute inhibitory projections to the central nucleus (CEA), the main output station of the amygdala for conditioned fear responses. Thus, after extinction training, ITC cells could reduce the impact of conditioned-stimulus-related BLA inputs to the CEA by means of feed-forward inhibition. Here we test the hypothesis that ITC neurons mediate extinction by lesioning them with a toxin that selectively targets cells expressing micro-opioid receptors (microORs). Electron microscopic observations revealed that the incidence of microOR-immunoreactive synapses is much higher in ITC cell clusters than in the BLA or CEA and that microORs typically have a post-synaptic location in ITC cells. In keeping with this, bilateral infusions of the microOR agonist dermorphin conjugated to the toxin saporin in the vicinity of ITC neurons caused a 34% reduction in the number of ITC cells but no significant cell loss in surrounding nuclei. Moreover, ITC lesions caused a marked deficit in the expression of extinction that correlated negatively with the number of surviving ITC neurons but not CEA cells. Because ITC cells exhibit an unusual pattern of receptor expression, these findings open new avenues for the treatment of anxiety disorders.     

Experimentally induced alteration in the polarity of developing neurons

Despite the great diversity of shapes exhibited by different classes of nerve cells, nearly all neurons share one feature in that they have a single axon and several dendrites. The two types of processes differ in their morphology, in their rate of growth, in the macromolecular composition of their cytoskeletons and surface membranes, and in their synaptic polarity. When hippocampal neurons are dissociated from the embryonic brain and cultured, they reproducibly establish this basic form with a single axon and several dendrites, despite the absence of any spatially organized environmental cues, and without the need for cell to cell contact. We have cut the axons of young hippocampal neurons within a day of their development: in some cases the initial axon regenerated, but more frequently one of the other processes, which if undisturbed would have become a dendrite, instead became the axon. Frequently the stump of the original axon persisted following the transection and subsequently became a dendrite. Evidently the neuronal processes that first develop in culture have the capacity to form either axons or dendrites. The acquisition of axonal characteristics by one neuronal process apparently inhibits the others from becoming axons, so they subsequently become dendrites.     

普通高校扩招给成人教育带来的机遇、挑战以及发展对策

随着前几年普通高校的持终扩招，我国高等教育进入了一个跨越式的发展阶段，普校扩招对成人教育而言是新的挑战和发展机遇，我们要理清思路，研究对策，树立新的教育思想观念，促进成人高等教育的可持续发展，为社会培养更多具有创新能力的有用人才。     

基于视觉的小型垂直起降UAV降落引导技术

为了使小型无人飞行器在执行任务过程中进行全程自动飞行,提出一种基于快速地面定位目标识别,与多目标尺寸视觉测量,使用Intel公司的开源图像处理库OpenCV进行高速实时图像处理,获取飞行器相对高度等信息以辅助引导小型无人飞行器自动降落的方法.     

拦截机动目标的一种鲁棒末制导律设计

为拦截空间机动目标,将目标的机动加速度视为外界干扰,建立纵向平面内拦截器与目标间非线性相对运动的动力学模型;用反馈线性化与线性H∞理论相结合的方法,设计了一种新的鲁棒末制导律,并通过数字仿真结果验证了该末制导律的有效性。该末制导律对外界干扰具有较强的鲁棒性,既可在目标以多种形式机动逃逸时使拦截器能以特定速度直接撞击目标,还可使拦截过程中拦截器与目标的视线角速度保持在较小的数值范围。同时,文中的方法避免了应用非线性H∞理论求解Hamilton-Jacobi-Issacs偏微分不等式的烦琐,简化了求解过程。     

Revealing structure and assembly cues for Arabidopsis root-inhabiting bacterial microbiota

The plant root defines the interface between a multicellular eukaryote and soil, one of the richest microbial ecosystems on Earth. Notably, soil bacteria are able to multiply inside roots as benign endophytes and modulate plant growth and development, with implications ranging from enhanced crop productivity to phytoremediation. Endophytic colonization represents an apparent paradox of plant innate immunity because plant cells can detect an array of microbe-associated molecular patterns (also known as MAMPs) to initiate immune responses to terminate microbial multiplication. Several studies attempted to describe the structure of bacterial root endophytes; however, different sampling protocols and low-resolution profiling methods make it difficult to infer general principles. Here we describe methodology to characterize and compare soil- and root-inhabiting bacterial communities, which reveals not only a function for metabolically active plant cells but also for inert cell-wall features in the selection of soil bacteria for host colonization. We show that the roots of Arabidopsis thaliana, grown in different natural soils under controlled environmental conditions, are preferentially colonized by Proteobacteria, Bacteroidetes and Actinobacteria, and each bacterial phylum is represented by a dominating class or family. Soil type defines the composition of root-inhabiting bacterial communities and host genotype determines their ribotype profiles to a limited extent. The identification of soil-type-specific members within the root-inhabiting assemblies supports our conclusion that these represent soil-derived root endophytes. Surprisingly, plant cell-wall features of other tested plant species seem to provide a sufficient cue for the assembly of approximately 40% of the Arabidopsis bacterial root-inhabiting microbiota, with a bias for Betaproteobacteria. Thus, this root sub-community may not be Arabidopsis-specific but saprophytic bacteria that would naturally be found on any plant root or plant debris in the tested soils. By contrast, colonization of Arabidopsis roots by members of the Actinobacteria depends on other cues from metabolically active host cells.     

Microfluidic single-cell coating with defined chemomechanical cues for cell therapy

Cell surface coating is an emerging technology that represents one of the most popular methods for cell engineering.Cell engi-neering refers to a series of tech...     

Clusters of iron-rich cells in the upper beak of pigeons are macrophages not magnetosensitive neurons

Understanding the molecular and cellular mechanisms that mediate magnetosensation in vertebrates is a formidable scientific problem. One hypothesis is that magnetic information is transduced into neuronal impulses by using a magnetite-based magnetoreceptor. Previous studies claim to have identified a magnetic sense system in the pigeon, common to avian species, which consists of magnetite-containing trigeminal afferents located at six specific loci in the rostral subepidermis of the beak. These studies have been widely accepted in the field and heavily relied upon by both behavioural biologists and physicists. Here we show that clusters of iron-rich cells in the rostro-medial upper beak of the pigeon Columbia livia are macrophages, not magnetosensitive neurons. Our systematic characterization of the pigeon upper beak identified iron-rich cells in the stratum laxum of the subepidermis, the basal region of the respiratory epithelium and the apex of feather follicles. Using a three-dimensional blueprint of the pigeon beak created by magnetic resonance imaging and computed tomography, we mapped the location of iron-rich cells, revealing unexpected variation in their distribution and number--an observation that is inconsistent with a role in magnetic sensation. Ultrastructure analysis of these cells, which are not unique to the beak, showed that their subcellular architecture includes ferritin-like granules, siderosomes, haemosiderin and filopodia, characteristics of iron-rich macrophages. Our conclusion that these cells are macrophages and not magnetosensitive neurons is supported by immunohistological studies showing co-localization with the antigen-presenting molecule major histocompatibility complex class II. Our work necessitates a renewed search for the true magnetite-dependent magnetoreceptor in birds.     

RGM is a repulsive guidance molecule for retinal axons

Axons rely on guidance cues to reach remote targets during nervous system development. A well-studied model system for axon guidance is the retinotectal projection. The retina can be divided into halves; the nasal half, next to the nose, and the temporal half. A subset of retinal axons, those from the temporal half, is guided by repulsive cues expressed in a graded fashion in the optic tectum, part of the midbrain. Here we report the cloning and functional characterization of a membrane-associated glycoprotein, which we call RGM (repulsive guidance molecule). This molecule shares no sequence homology with known guidance cues, and its messenger RNA is distributed in a gradient with increasing concentration from the anterior to posterior pole of the embryonic tectum. Recombinant RGM at low nanomolar concentration induces collapse of temporal but not of nasal growth cones and guides temporal retinal axons in vitro, demonstrating its repulsive and axon-specific guiding activity.     

面向对象数据库通用性研究

本文首先介绍了面向对象数据库在新型数据库应用中的优势,以及实现面向对象数据库的方法,然后采用在关系数据库上添加面向对象接口的方法对图书流通管管理信息系统进行了分析和设计,最后从中总结出了面向对象数据库信息管理系统开发的一般性通用规律。     

彩色多普勒超声引导穿刺技术的临床应用价值

目的：探讨彩色多普勒超声在引导临床穿刺操作中的影响因素,旨在提高彩色多普勒超声引导下临床穿刺的准确性和安全性。方法：对97例临床组织穿刺活检、囊性病变硬化治疗以及含液性病灶穿刺引流中彩色多普勒超声引导穿刺情况进行分析。结果：应用彩色多普勒超声对97例临床穿刺进行引导,91例达到临床穿刺的预期目的,成功率93.81%。彩色多普勒超声引导中探头选择、穿刺针和针架、穿刺引导线以及病灶大小是影响穿刺成功的重要因素。结论：彩色多普勒超声引导对提高临床穿刺准确性和安全性具有重要的价值。     

应用动态逆理论的反舰导弹规避机动导引律设计

为了提高反舰导弹的突防能力,有效规避敌方舰空导弹的拦截,完成精确打击目标的战术要求,从便于工程实现的角度出发,应用时标分离的方法,将弹目相对运动模型分离为2个一阶的动力学子系统,这2个子系统分别对应于视线角速率层(慢动力学系统)和自动驾驶仪惯性滞后层(快动力学系统),对这2个子系统分别进行动态逆控制设计,设计了一种能够...     

发展军队专业学位研究生教育的思考

随着军队使命任务的拓展以及建设信息化军队、打赢信息化战争战略目标的确立,军队建设对高层次应用型人才的需求不断增加,我军研究生教育结构目前暂时无法满足这一需求,因此急需大力发展专业学位研究生教育.简要分析了军队专业学位教育发展的困境,提出了新的建设思路,并重点从学科布局、招生选拔、导师建设、教学组织、学位规范和信息化管理等环节提出了具体的措施和方法.     

前视红外末制导Nprod目标识别算法适应性研究

描述了前视红外末制导景象匹配中归一化积相关(Nprod)目标识别算法的基本原理。由实际拍摄的典型目标前视红外图像匹配结果得出:当目标所占面积越大、与背景灰度反差越大、边缘越清晰,Nprod算法匹配效果越好;在目标与背景的灰度分布集中或者目标较远的情况下,匹配效果不甚理想。给出了Nprod目标识别算法的基准图预处理方法,对远距离情况下建筑物目标的匹配进行了匹配方法研究,实验表明具有较好的匹配效果。     

山东省公路网发展的分维数

针对以往公路网评价缺少几何总体性测度指标，引进分形几何学中分维数概念分析公路网。通过对山东省公路网的发展进行分维数研究，为山东省省道主干线公路网的发展，特别是高速公路网的发展提供了网络总体特征依据。     

快速原型法在MIS开发中的应用研究

研究了快速原型法在MIS开发中的应用 ,说明了快速原型法在开发MIS时所具有的优点 ,同时指出了快速原型法的不足及改进。     

管道展开图计算机绘制新方法

本文讨论对各种口径的管道进行改道、弯曲和开贫所涉及到的展开图计算机作图问题，通过数学变换能简便地绘出各种展开图，它有利于提高管道施工质量，缩短施工周期。