The stress experience dependent long-term depression disassociated with stress effect on spatial memory task

Behavioral stress can either block or facilitate memory and affect the induction of long-term potentiation (LTP) and long-term depression (LTD). However, the relevance of the stress experience-dependent long-term depression (SLTD) to spatial memory task is unknown. Here we have investigated the effects of acute and sub-acute elevated platform (EP) and foot shock (FS) stress on LTD induction in CA1 region of the hippocampus of anesthetized rats and spatial memory in Morris water maze. We found that LTD was facilitated by acute EP stress, but not by sub-acute EP stress that may be due to the fast adaptation of the animals to this naturalistic mild stress. However, FS stress, an inadaptable strong stress, facilitated LTD induction both in acute and sub-acute treatment. In addition, with the same stress protocols, acute EP stress impaired spatial memory but the sub-acute EP stressed animals performed the spatial memory task as well as the controls, may due to the same reason of adaptation. However, acute FS stress slightly impaired learning but sub-acute FS even enhanced memory retrieval. Our results showed that SLTD was disassociated with the effect of stress on memory task but might be related to stress experience-dependent form of aberrant memory. (C) 2003 Elsevier Science Ireland Ltd. and the Japan Neuroscience Society. All rights reserved.

γ-氨基丁酸受体和甘氨酸受体在大鼠丙泊酚麻醉中的作用

目的 研究丙泊酚对大鼠海马CA1区电刺激诱发兴奋性突触后电流(EPSC)的影响,分析γ-氨基丁酸(GABA)受体和甘氨酸受体在丙泊酚麻醉中的作用.方法 断头法分离wistar大鼠(13～19 d)海马半脑,切出400 μm厚度的海马脑片,全细胞膜片钳技术记录CA1区锥体神经元EPSC.80张脑片分为八组:脂肪乳剂组,50 μmol/L丙泊酚组,100 μmol/L丙泊酚组,200 μmol/L丙泊酚组,SR95531组,士的宁组,SR95531+100 μmol/L丙泊酚组,士的宁+100 μmol/L丙泊酚组,每组10张.SR95531+100 μmol/L丙泊酚组和士的宁+100 μmol/L丙泊酚组先在循环液中加入10 μmol/L SR95531或4 μmol/L士的宁预孵脑片30 min.八组均记录基础EPSC 10 min,然后加入不同药物,继续记录EPSC 40 min.膜钳制电压为-70 mV.结果 脂肪乳剂、SR95531和士的宁对EP-SC幅值无影响;丙泊酚呈剂量依赖性的抑制EPSC幅值,50、100、200 μmol/L丙泊酚最大抑制EPSC幅值为14.4%、52.3%、67.8%;SR95531+100 μmol/L丙泊酚组加入丙泊酚后,EPSC幅值基本无改变;士的宁+100 μmol/L丙泊酚组加入丙泊酚后,EPSC幅值仍然下降,最大抑制程度为34.7%.结论 丙泊酚主要通过增强GABAA受体功能使兴奋性突触活动降低,甘氨酸受体在其中起到协同和调节作用.

The effect of acute stress on LTP and LTD induction in the hippocampal CA1 region of anesthetized rats at three different ages

Not all experiences are memorized equally well. Especially, some types of stress are unavoidable in daily life and the stress experience can be memorized for life. Previous evidence has showed that synaptic plasticity, such as long-term potentiation (LTP) that may be the major cellular model of the mechanism underlying learning and memory, is influenced by behavioral stress. However, the effect of behavioral stress on age-related synaptic plasticity in-vivo was primarily known. Here we found that the LTP induction in the hippocampal CA1 region of anesthetized rats obviously showed inverted-U shape related to ages (4, 10 and 74 weeks old rats), but low-frequency stimulation was unable to induce reliable long-term depression (LTD) in these animals. Furthermore, acute elevated platform (EP) stress enabled reliable LTD significantly and completely blocked LTP induction at these ages. Importantly, LTD after exposure to acute EP stress showed similar magnitude over these ages. The present results that stress enables LTD but impairs LTP induction at these three ages strengthen a view that stress experience-dependent LTD (SLTD) may underlie stress form of aberrant memories. (C) 2004 Elsevier B.V. All rights reserved.

Robust estimation of local genetic ancestry in admixed populations using a nonparametric Bayesian approach.

We present a new haplotype-based approach for inferring local genetic ancestry of individuals in an admixed population. Most existing approaches for local ancestry estimation ignore the latent genetic relatedness between ancestral populations and treat them as independent. In this article, we exploit such information by building an inheritance model that describes both the ancestral populations and the admixed population jointly in a unified framework. Based on an assumption that the common hypothetical founder haplotypes give rise to both the ancestral and the admixed population haplotypes, we employ an infinite hidden Markov model to characterize each ancestral population and further extend it to generate the admixed population. Through an effective utilization of the population structural information under a principled nonparametric Bayesian framework, the resulting model is significantly less sensitive to the choice and the amount of training data for ancestral populations than state-of-the-art algorithms. We also improve the robustness under deviation from common modeling assumptions by incorporating population-specific scale parameters that allow variable recombination rates in different populations. Our method is applicable to an admixed population from an arbitrary number of ancestral populations and also performs competitively in terms of spurious ancestry proportions under a general multiway admixture assumption. We validate the proposed method by simulation under various admixing scenarios and present empirical analysis results from a worldwide-distributed dataset from the Human Genome Diversity Project.

The effect of remodelling and contractility of the actin cytoskeleton on the shear resistance of single cells: a computational and experimental investigation.

The biomechanisms that govern the response of chondrocytes to mechanical stimuli are poorly understood. In this study, a series of in vitro tests are performed, in which single chondrocytes are subjected to shear deformation by a horizontally moving probe. Dramatically different probe force-indentation curves are obtained for untreated cells and for cells in which the actin cytoskeleton has been disrupted. Untreated cells exhibit a rapid increase in force upon probe contact followed by yielding behaviour. Cells in which the contractile actin cytoskeleton was removed exhibit a linear force-indentation response. In order to investigate the mechanisms underlying this behaviour, a three-dimensional active modelling framework incorporating stress fibre (SF) remodelling and contractility is used to simulate the in vitro tests. Simulations reveal that the characteristic force-indentation curve observed for untreated chondrocytes occurs as a result of two factors: (i) yielding of SFs due to stretching of the cytoplasm near the probe and (ii) dissociation of SFs due to reduced cytoplasm tension at the front of the cell. In contrast, a passive hyperelastic model predicts a linear force-indentation curve similar to that observed for cells in which the actin cytoskeleton has been disrupted. This combined modelling-experimental study offers a novel insight into the role of the active contractility and remodelling of the actin cytoskeleton in the response of chondrocytes to mechanical loading.

Restricting exchangeable nonparametric distributions

Distributions over exchangeable matrices with infinitely many columns, such as the Indian buffet process, are useful in constructing nonparametric latent variable models. However, the distribution implied by such models over the number of features exhibited by each data point may be poorly- suited for many modeling tasks. In this paper, we propose a class of exchangeable nonparametric priors obtained by restricting the domain of existing models. Such models allow us to specify the distribution over the number of features per data point, and can achieve better performance on data sets where the number of features is not well-modeled by the original distribution.

水霉菌总DNA提取方法研究

本实验采用EP管反复冻融和研磨的破壁方式,利用溶菌酶法、CTAB法、改良CTAB法、尿素法、十二烷基硫酸钠(SDS)法等5种方法,分别对5种鱼类致病性水霉菌(寄生水霉、多子水霉、异株水霉及两未定种)的基因组DNA进行提取,并采用紫外分光光度计和ITS区基因(包括5.8SrDNA)PCR扩增对DNA进行了评价。紫外分光光度计检测结果表明,5种方法均可提取到水霉菌DNA,其中改良CTAB法提取的5种水霉菌的DNA产量和质量最高,A260/A280在1.79—1.82之间,浓度为45μg/mL;PCR检测结果表

Effects of dietary cyanobacteria of two different sources on growth and recovery of hybrid tilapia (Oreochromis niloticus x O. aureus)

A 115 days feeding trial was conducted to evaluate the effect of dietary cyanobacteria on growth, microcystins (MCs) accumulation in hybrid tilapia (Oreochromis niloticus x O. aureus) and the recovery when the fish were free of cyanobacteria. Three experimental diets were formulated: the control (cyanobacteria free diet); one test diet with cyanobacteria from Lake Taihu (AMt 80.0 mu g MCs g(-1) diet) and one with cyanobacteria from Lake Dianchi (AMd, 410.0 rho g MCs g(-1) diet). Each diet was fed to fish for 60 days and then all fish were free of cyanobacteria for another 55 days. A significant increase in feeding rate (FR) was observed in fish fed AMd diet after a first 30-day exposure (1(st) EP), and in fish fed both AMt diet and AMd diet after a second 30-day exposure (2(nd) EP). Specific growth rates (SGR) of fish fed AMt diet and AMd diet were both obviously affected after the first 30-day exposure, but SGR was only significantly affected in fish fed AMt diet after the second 30-day exposure. After a 55-day recovery, there were no significant differences among diets in the indices mentioned above. Much higher concentrations of MCs were accumulated in tissues of all fish exposed to cyanobacteria. After the 55-day recovery, MC concentrations in fish tissues were significantly lower than those on day 60. (C) 2009 Elsevier Ltd. All rights reserved.

Effects of Sb, N, and period on the electronic properties of GaAs/GaInNAsSb superlattices

We have calculated the bond distributions and atom positions of GaAs/GalnNAsSb superlattices using Keating's semiempirical valence force field (VFF) model and Monte Carlo simulation. The electronic structures of the superlattices are calculated using folded spectrum method (FSM) combined with an empirical pseudopotential (EP) proposed by Williamson et al.. The effects of N and Sb on superlattice energy levels are discussed. We find that the deterioration of the optical properties induced by N can be explained by the localization of the conduction-band states around the N atom. The electron and hole effective masses of the superlattices are calculated and compared with the effective masses of the bulk GaAs and GaInAs.

Disentangling mechanical and mass effects on nanomechanical resonators

Micro and nanomechanical resonators are powerful and label-free sensors of analytes in various environments. Their response, however, is a convolution of mass, rigidity, and nanoscale heterogeneity of adsorbates. Here we demonstrate a procedure to disentangle this complex sensor response, to simultaneously measure both mass and elastic properties of nanometer thick samples. This turns an apparent disadvantage of these resonators into a striking and unique asset, enabling them to measure more than mass alone.

应激对大鼠海马突触可塑性和学习记忆的影响

突触可塑性参与学习记忆，是学习记忆过程中必不可少的重要环节。应激能损伤或提高学习记忆、抑制长时程增强（Long一termPotentiation，LTP）、易化长时程抑制（Long一termdePressfon，LTD）。然而，应激经历依赖的长时程抑制（StressexperiencedePendentLTD，SLTD）在学习记忆中有什么意义还不清楚，这正是本文首先要探讨问题。其次，尽管我们在不同年龄时期的学习记忆能力不同，但是对所经历的重大应激事件仍然能产生牢固的记忆，这就有必要进一步通过阐明应激对突触可塑性的影响是否有年龄差异来解释SLTD的意义。再者，我们甚至不清楚为什么有的时候应激损伤学习记忆而有的时候又提高学习记忆。为了阐明这个问题，本文在最后一部分研究了哪些因素决定应激损伤还是提高学习记忆。为了探讨SLTD与学习记忆的关系，我们在第一部分实验中研究急性或亚急性的高台（ElevatedPlatform，EP）或足部电击（Footshock，Fs）对4周龄诚star大鼠海马CAI区LTD诱导的影响，以及这些应激条件对大鼠空间学习记忆的影响。结果显示：（l）急性EP易化LTD，亚急性EP不易化LTD；急性和亚急性FS都易化了LTD。（2）急性EP损伤空间记忆，亚急性EP对空间记忆没有影响；急性FS不影响空间记忆，亚急性FS却提高了空间记忆。这部分的实验结果表明：sLTD存在与否与应激对空间记忆的影响不是一一对应的关系，提示sLTD可能参与了应激记忆（对应激经历产生的记忆）。如果SLTD参与应激记忆，那么，研究应激对突触可塑性的影响是否有年龄依赖性将有助于解释不同年龄时期的学习记忆能力不同但是都能牢固记忆应激事件这一现象。为此，我们在第二部分实验中进一步研究EP对幼年、中年和老年动物（4，10和74周龄的Wistar大鼠）海马CAI区LTP／LTD诱导的影响。结果表明：（1）没有应激的情况下，LTP的大小随动物年龄的增加呈明显的倒U型关系，而低频刺激都不能诱导出LTD。（2）EP易化了这些年龄段大鼠的LTD，并完全阻断它们的LTP。值得注意的是，在三个年龄段大鼠中，EP易化的LTD大小一样。该部分实验结果提示：SLTD没有年龄依赖性，这与人和动物在不同年龄时期对所受到的重大应激事件都能产生牢固记忆这一现象相一致。所以，该部分结果进一步加强了第一部分结果的推测：SLTD参与应激记忆。应激有的时候提高动物的空间记忆能力，有的时候又损伤其空间记忆。为了阐明是什么因素决定应激损伤还是提高学习记忆，我们在第三部分实验中研究EP、FS和水迷宫游泳应激经历对六个年龄段动物（4，10，13，20，67，76周龄）在水迷宫任务中的影响。结果显示：（l）EP应激损伤无水迷宫游泳应激经历大鼠的空间记忆。（2）EP应激提高有游泳应激经历幼年大鼠的空间记忆；训练前外源性补充皮质酮或FS都抑制皮质酮或FS导致的空间记忆受损。（3）糖皮质激素受体的拮抗剂RU38486阻断上述的空间记忆成绩提高。所以，不同的应激经历和动物年龄两个因素共同决定了应激损伤还是提高学习记忆。

长白山阔叶红松林生产力对气候变化响应的模拟研究

本论文以长白山阔叶红松林为研究对象，观测了阔叶红松林主要树种的光合生理生态特征，建立了单叶化汁卜片的光合作用模型，上推出群落的生产力模型，采用基于干物质生产过程的模型Sim-CYCLE，模型了该生态系统对·气候变化的响应。得到主要结论如下：（1）、在不同的CO2浓度和光合有效辐射条件下，长白山阔价卜红松林主要树种净光合速率月动态规律不同；气孔导度随着瞬时光合有效辐射强度和C02浓度的增加而有下降趋势。（2）、建立的适用于阔价f一红松林的单叶化气孔导度对环境因子气温（Ta）、光合有效辐射（PAR）、饱和水汽压（VPD）的响应模型：gs＝PAR（-1.606Ta2＋118.192Ta＋1878.67）／（355.700+PAR）（-430.433+VPL），这是一个基于叶片光合机理的群落生产力模型，在模拟了长白山阔叶红松林群落生产力时取得了满意的效果。（3）、采用干物质产量理论的Sim-CYCLE模型，通过样地尺度的参数化模拟表明，长白山阔叶红松林生态系统的总初级生产力（GPP）为14.89Mgcha-1、净初级生产力（NPP）为8.22MgCha-1、净生态系统生产力困EP）为2．67MgCha-1；在CO2倍增和温度上升时碳积累在增加，净初级生产力（NPP）为9.03±1.51MgCha-1、净生态系统生产力（NEP）为2.95±0.47MgCha-1。

O~(3+)与H_2碰撞中非解离电荷转移过程的全量子计算

应用全量子的分子轨道强耦合方法,研究了基态的O3+(2s22p2P)与氢分子碰撞的非解离电荷转移过程,计算了不同方位角(25°,45°,89°),能量分别为100,500,1000和5000eV/u时的单电子俘获的振动分辨的态选择截面及相应的微分截面.分子轨道强耦合计算中采用了自旋耦合价带理论计算的三原子分子势能面和径向耦合矩阵元.对氢分子的自身转动,采用无限阶的冲量近似方法;对体系的电子运动同H2或H2+的振动之间的耦合,采用了振动冲量近似.结果发现,对不同的入射能量,振动态选择截面随振动量子数的分布发生了一定的改变;不同入射能量和不同方位角的振动态分辨的微分截面具有类似的结构,在极小的散射角附近出现一个最大值平台,然后散射截面随着散射角的增大而减小,并出现大量的震荡结构,其中第一个震荡结构对应的散射角位置随入射能量Ep以Ep-1/2的标度规律变化;微分截面的结构和大小对H2方位角α的变化敏感,这种性质为H2取向的诊断提供了一种可能的途径.

Theoretical investigation on excitation, ionization and capture in H(1s, 2s)+H(1s, 2s) collisions

Cross sections of electron- loss in H( 1s)+ H( 1s) collisions and total collisional destruction of H( 2s) in H( 1s) + H( 2s) collisions are calculated by four- body classical- trajectory Monte Carlo ( CTMC) method and compared with previous theoretical and experimental data over the energy range of 4 - 100 keV. For the former a good agreement is obtained within di. erent four- body CTMC calculations, and for the incident energy Ep > 10 keV, comparison with the experimental data shows a better agreement than the results calculated by the impact parameter approximation. For the latter, our theory predicts the correct experimental behaviour, and the discrepancies between our results and experimental ones are less than 30%. Based on the successive comparison with experiments, the cross sections for excitation to H( 2p), single- and double- ionization and H- formation in H( 2s)+ H( 2s) collisions are calculated in the energy range of 4 - 100 keV for the. rst time, and compared with those in H( 1s)+ H( 1s) and H( 1s)+ H( 2s) collisions.