早产儿脑损伤和脑发育的临床及MRI分析

目的:探讨核磁共振成像(Magnetic Resonance Imaging,MRI)在早产儿脑损伤及脑发育中的临床诊断价值及影响早产儿脑损伤的危险因素.方法:选取44例早产儿,在纠正胎龄40周进行头颅MRI检查,并进行大脑发育成熟度的MRI评分.在纠正胎龄3月时行盖泽尔(GESELL)智能发育检测,同时结合临床危险因素分析.结果:1纠正胎龄40周MRI结果发现早产儿有脑损伤27例,足月儿未发现脑损伤.2早产儿脑损伤组、早产儿无脑损伤组及对照组大脑发育成熟度评分通过方差分析三组平均值比较差异均有统计学意义(P0.05).3大脑发育成熟度的MRI评分各项评分点比较,早产儿脑损伤组与早产儿无脑损伤组在大脑卷曲程度、髓鞘化程度和胶质细胞迁移带方面得分有统计学差异(P0.05),胚胎基质残余方面得分无统计学差异(P0.05).4神经发育落后组、神经发育正常组与神经发育聪明组的大脑发育成熟度的MRI评分三组间比较有统计学意义(P0.05).5Logistic多元逐步回归法分析,产前因素及产后因素中机械通气、脐带异常、生后1分钟Apgar评分低、分娩方式是早产儿发生脑损伤的高危险因素(P0.05).结论:MRI是评价新生儿脑损伤的有效手段,大脑发育成熟度的MRI评分对预测早产儿远期神经发育有重要意义.早产儿脑损伤是多种因素相互作用的结果,机械通气、脐带异常、窒息与早产儿脑损伤有密切关系.     

Brain potential and functional MRI evidence for how to handle two languages with one brain

Bilingual individuals need effective mechanisms to prevent interference from one language while processing material in the other. Here we show, using event-related brain potentials and functional magnetic resonance imaging (fMRI), that words from the non-target language are rejected at an early stage before semantic analysis in bilinguals. Bilingual Spanish/Catalan and monolingual Spanish subjects were instructed to press a button when presented with words in one language, while ignoring words in the other language and pseudowords. The brain potentials of bilingual subjects in response to words of the non-target language were not sensitive to word frequency, indicating that the meaning of non-target words was not accessed in bilinguals. The fMRI activation patterns of bilinguals included a number of areas previously implicated in phonological and pseudoword processing, suggesting that bilinguals use an indirect phonological access route to the lexicon of the target language to avoid interference.     

Intrinsic functional architecture in the anaesthetized monkey brain

The traditional approach to studying brain function is to measure physiological responses to controlled sensory, motor and cognitive paradigms. However, most of the brain's energy consumption is devoted to ongoing metabolic activity not clearly associated with any particular stimulus or behaviour. Functional magnetic resonance imaging studies in humans aimed at understanding this ongoing activity have shown that spontaneous fluctuations of the blood-oxygen-level-dependent signal occur continuously in the resting state. In humans, these fluctuations are temporally coherent within widely distributed cortical systems that recapitulate the functional architecture of responses evoked by experimentally administered tasks. Here, we show that the same phenomenon is present in anaesthetized monkeys even at anaesthetic levels known to induce profound loss of consciousness. We specifically demonstrate coherent spontaneous fluctuations within three well known systems (oculomotor, somatomotor and visual) and the 'default' system, a set of brain regions thought by some to support uniquely human capabilities. Our results indicate that coherent system fluctuations probably reflect an evolutionarily conserved aspect of brain functional organization that transcends levels of consciousness.     

龟纹瓢虫对菊小长管蚜的捕食功能反应

试验研究了龟纹瓢虫对菊小长管蚜的捕食功能反应。结果表明，在恒温25℃，相对湿度80％的条件下，龟纹瓢虫成虫捕食菊小长管蚜末龄若虫或成虫的功能反应为HollingⅡ型反应，其捕食反应的功能方程为：1／Na=0．9609x(1／N) 0．00855，在一昼夜里，一头瓢虫的最大捕食量为117．0头，捕食一头蚜虫需0．00855d。     

Latent synaptic pathways revealed after tetanic stimulation in the hippocampus

Synaptic plasticity may result from changes at existing synapses or from alterations in the number of functional synaptic connections. In the hippocampus excitatory synaptic strength is persistently enhanced after tetanic stimulation. Here we report that latent synaptic pathways may also become functional. Simultaneous intracellular recordings were made from pairs of CA3 pyramidal cells in slices from guinea pig hippocampus. After stimulating afferent fibres repetitively, polysynaptic excitatory pathways between previously unconnected cells became apparent. The efficacy of recurrent inhibitory circuits was also reduced. The loss of inhibitory control is of interest because latent excitatory pathways are revealed after pharmacological suppression of inhibition. This plasticity in local synaptic circuits leads to the emergence of synchronous firing in groups of CA3 cells. The formation of groups of associated cells and the ability of some cells to initiate synchronous firing in a larger cell group through recurrent pathways is reminiscent of several models of information storage and recall in the cortex.     

静息态脑功能成像评价平衡针对正常人的中枢作用

目的:应用静息态脑功能磁共振成像技术,探讨平衡针的中枢作用机制.方法:选择10名健康志愿者,于针刺平衡针前后分别进行磁共振腩功能成像扫描,应用功能连接方法处理功能磁共振(fMRI)成像数据,针刺前后两组数据采用组间配对t检验统计分析.结果:针刺后的双侧颞中回、双侧眶上同、双侧尾状核头、双侧岛叶、左侧腹背侧核、双侧额上回...     

The GlobalStability of Predator-Prey System of Gause-Type with Holling Ⅲ Functional Response

This paper deals with the question of global stability of the positive locally asymptotically stable equilibrium in a class of predator-prey system of Gause-type with Holling III functional response. The Dulac's criterion is applied and liapunov functions are constructed to establish the global stability. Foundation item: Supported by the National Natural Science Foundation of China (19531070) Biography: Feng Jian-wen (1964-), male, Ph. D candidate, research interests: the qualitative theory and bifurcation theory of ODE.     

Sleep is of the brain, by the brain and for the brain

Sleep is a widespread biological phenomenon, and its scientific study is proceeding at multiple levels at the same time. Marked progress is being made in answering three fundamental questions: what is sleep, what are its mechanisms and what are its functions? The most salient answers to these questions have resulted from applying new techniques from basic and applied neuroscience research. The study of sleep is also shedding light on our understanding of consciousness, which undergoes alteration in parallel with sleep-induced changes in the brain.     

两自由度局部非线性系统的脉冲响应时域法

将两自由度局部非线性振动系统的非线性弹簧力和阻尼力等效成外力,建立数学模型,将线性振动系统的脉冲响应时域法应用于该振动系统,通过对应线性系统的单位脉冲响应与等效非线性力的卷积积分,得到局部非线性振动系统的响应;对该模型进行了数值仿真．实验模型测试结果验证了该方法在局部非线性振动系统领域的可行性,为求解具有局部非线性的大型机械系统的振动响应提供了一种新的思路．     

The formation of cluster elliptical galaxies as revealed by extensive star formation

The most massive galaxies in the present-day Universe are found to lie in the centres of rich clusters. They have old, coeval stellar populations suggesting that the bulk of their stars must have formed at early epochs in spectacular starbursts, which should be luminous phenomena when observed at submillimetre wavelengths. The most popular model of galaxy formation predicts that these galaxies form in proto-clusters at high-density peaks in the early Universe. Such peaks are indicated by massive high-redshift radio galaxies. Here we report deep submillimetre mapping of seven high-redshift radio galaxies and their environments. These data confirm not only the presence of spatially extended regions of massive star-formation activity in the radio galaxies themselves, but also in companion objects previously undetected at any wavelength. The prevalence, orientation, and inferred masses of these submillimetre companion galaxies suggest that we are witnessing the synchronous formation of the most luminous elliptical galaxies found today at the centres of rich clusters of galaxies.     

A functional correlate for the dihydropyridine binding site in rat brain

Calcium channels, controlling the influx of extracellular Ca2+ and hence neurotransmitter release, exist in the brain. However, drugs classed as calcium antagonists and which inhibit Ca2+ entry through voltage-activated Ca2+ channels in heart and smooth muscle, seem not to affect any aspect of neuronal function in the brain at pharmacologically relevant concentrations. Yet the dihydropyridine calcium antagonists (for example, nitrendipine) bind stereospecifically with high affinity to a recognition site on brain-cell membranes thought to represent the Ca2+ channel and consequently, the physiological relevance of these sites has been questioned. However, activation of voltage-dependent Ca2+ channels can increase cytoplasmic Ca2+ and neurotransmitter release in neuronal tissue. We show here that Bay K8644, a dihydropyridine Ca2+-channel activator, can augment K+-stimulated release of serotonin from rat frontal cortex slices and that these effects can be antagonized by low concentrations of calcium antagonists. As 3H-dihydropyridine binding to cortical membrane preparations resembles the binding in heart and smooth muscle where there are good functional correlates we conclude that the dihydropyridine binding sites in the brain represent functional Ca2+ channels that can be unmasked under certain circumstances.     

Differentiation of the asteroid Ceres as revealed by its shape

The accretion of bodies in the asteroid belt was halted nearly 4.6 billion years ago by the gravitational influence of the newly formed giant planet Jupiter. The asteroid belt therefore preserves a record of both this earliest epoch of Solar System formation and variation of conditions within the solar nebula. Spectral features in reflected sunlight indicate that some asteroids have experienced sufficient thermal evolution to differentiate into layered structures. The second most massive asteroid--4 Vesta--has differentiated to a crust, mantle and core. 1 Ceres, the largest and most massive asteroid, has in contrast been presumed to be homogeneous, in part because of its low density, low albedo and relatively featureless visible reflectance spectrum, similar to carbonaceous meteorites that have suffered minimal thermal processing. Here we show that Ceres has a shape and smoothness indicative of a gravitationally relaxed object. Its shape is significantly less flattened than that expected for a homogeneous object, but is consistent with a central mass concentration indicative of differentiation. Possible interior configurations include water-ice-rich mantles over a rocky core.     

Molecular operations of the sodium-calcium exchanger revealed by conformation currents

The sodium-calcium exchanger is critical in the normal functioning of many cells. In heart muscle, it is the principal way by which the cells keep the concentration of intracellular calcium low, pumping out the Ca2+ that enters the cytosol through L-type Ca2+ channels. The exchanger may also contribute to the triggering of Ca2+ release during voltage-activated excitation-contraction coupling in heart. Time resolved examination of the conformational changes of macromolecules in living cells has so far been largely restricted to ion-channel proteins whose gating is voltage-dependent. We have now directly measured electrical currents arising from the molecular rearrangements of the sarcolemmal Na-Ca exchanger. Changes in the conformation of the exchanger protein were activated by a rapid increase in the intracellular calcium concentration produced by flash photolysis of caged calcium in voltage-clamped heart cells. Two components of membrane current were produced, reflecting a calcium-dependent conformational change of the transporter proteins and net transport of ions by the exchanger. The properties of these components provide evidence that the Na-Ca exchanger protein undergoes two consecutive membrane-crossing molecular transitions that each move charge, and that there are at least 250 exchangers per micron 2 turning over up to 2,500 times per second.     

具有HollingⅢ型功能反应的捕食与被捕食收获模型的分支与极限环

研究了具有HollingⅢ型功能反应的捕食与被捕食模型在非线性状态反馈收获下所呈现的复杂性态.在给定生物参数与控制参数满足一定条件下,讨论了该模型正平衡点的存在惟一性及其渐近稳定性,分析了产生分支的原因,证明了极限环的存在性.     

Biosignatures as revealed by spectropolarimetry of Earthshine

Low-resolution intensity spectra of Earth's atmosphere obtained from space reveal strong signatures of life ('biosignatures'), such as molecular oxygen and methane with abundances far from chemical equilibrium, as well as the presence of a 'red edge' (a sharp increase of albedo for wavelengths longer than 700?nm) caused by surface vegetation. Light passing through the atmosphere is strongly linearly polarized by scattering (from air molecules, aerosols and cloud particles) and by reflection (from oceans and land). Spectropolarimetric observations of local patches of Earth's sky light from the ground contain signatures of oxygen, ozone and water, and are used to characterize the properties of clouds and aerosols. When applied to exoplanets, ground-based spectropolarimetry can better constrain properties of atmospheres and surfaces than can standard intensity spectroscopy. Here we report disk-integrated linear polarization spectra of Earthshine, which is sunlight that has been first reflected by Earth and then reflected back to Earth by the Moon. The observations allow us to determine the fractional contribution of clouds and ocean surface, and are sensitive to visible areas of vegetation as small as 10 per cent. They represent a benchmark for the diagnostics of the atmospheric composition, mean cloud height and surfaces of exoplanets.     

bFGF对大鼠坐骨神经损伤后腓肠肌功能恢复的影响

目的：观察碱性成纤维细胞生长因子（ｂ Ｆ Ｇ Ｆ） 对大鼠坐骨神经损伤后腓肠肌功能恢复的作用。方法：以钳夹损伤左侧坐骨神经大鼠为模型,治疗组肌肉注射ｂ Ｆ Ｇ Ｆ,对照组注射等渗盐水,隔日１ 次。术后２ 、３ 、４ 周分别对治疗组和对照组损伤侧及健侧腓肠肌进行肌诱发电位及肌收缩力检测,以健侧为１００ ％ ,求出损伤侧各指标的恢复率。结果：与对照组相比,治疗组腓肠肌诱发电位幅值恢复率明显加快（ Ｐ＜ ００５） ;腓肠肌单收缩力和强直收缩力的恢复率也显著加强（ Ｐ＜ ００５ 和 Ｐ＜ ００１） 。结论：ｂ Ｆ Ｇ Ｆ 能促进大鼠坐骨神经损伤后骨骼肌运动功能的恢复     

一个具功能性反应的微分生态系统的定性分析

应用数学生态学和微分方程定性理论,建立并讨论了一个具功能性反应的微分生态系统,在给定参数满足一定条件下,证明了该系统极限环的存在性和惟一性,以及该系统的正平衡点全局渐近稳定.     

Glycine potentiates the NMDA response in cultured mouse brain neurons

Transmitters mediating 'fast' synaptic processes in the vertebrate central nervous system are commonly placed in two separate categories that are believed to exhibit no interaction at the receptor level. The 'inhibitory transmitters' (such as glycine and GABA) are considered to act only on receptors mediating a chloride conductance increase, whereas 'excitatory transmitters' (such as L-glutamate) are considered to activate receptors mediating a cationic conductance increase. The best known excitatory receptor is that specifically activated by N-methyl-D-aspartate (NMDA) which has recently been characterized at the single channel level. The response activated by NMDA agonists is unique in that it exhibits a voltage-dependent Mg block. We report here that this response exhibits another remarkable property: it is dramatically potentiated by glycine. This potentiation is not mediated by the inhibitory strychnine-sensitive glycine receptor, and is detected at a glycine concentration as low as 10 nM. The potentiation can be observed in outside-out patches as an increase in the frequency of opening of the channels activated by NMDA agonists. Thus, in addition to its role as an inhibitory transmitter, glycine may facilitate excitatory transmission in the brain through an allosteric activation of the NMDA receptor.