肌肉延迟性酸痛的神经生物学机制研究进展

肌肉延迟性酸痛(delayed onset muscle soreness, DOMS)是生活中经常遇到的一种现象,由于其发生机制尚不十分清楚,并缺乏可靠的防治措施,一直成为运动医学界的重要话题.本文总结了近年来有关DOMS发生机制方面的研究成果,着重从神经生物学角度来探讨和分析DOMS的产生原因.     

繁殖保障和延迟自交的研究进展

尽管植物在进化过程中面临不利自花授粉的选择,但许多植物仍维持混合的授粉机制。繁殖保障假说是解释自交进化的最重要因子之一,一直是植物生殖生态学和进化生物学关注的焦点之一。概述了近年来的主要研究热点及其进展,包括自交进化的遗传和生态机制及理论模型探讨、繁殖保障假说的提出、验证自交能否提供繁殖保障的例证、延迟自交的类型及延迟自交能否提供繁殖保障的例证等方面。介绍了我国在繁殖保障和延迟自交方面研究的现状和不足之处,结合国际上研究繁殖保障假说的发展趋势已由单季节、单种群、单因子的研究阶段过渡到多季节、多种群、多因子（自交方式及其所占比例、花粉折损、种子折损、自交率和近交衰退）的综合研究阶段,及由传统的、经典的研究方法过渡到应用现代实验手段（如SSR、SNP等分子标记）和先进仪器设备的研究阶段,提出今后研究中应注意的问题。有必要借用多学科（植物学、生态学和分子生物学）的方法及手段进行不同物种的对比和综合细致的研究。     

高山植物扁蕾的延迟自交机制

扁蕾(Gentianopsis barbata)具有鲜艳的花和显著的腺体,并且花开放的前5 d柱头和花药始终处于不同的位置(雌雄异位),这些花综合征表明该植物应为异花传粉。为检验这一假设,我们对青藏高原植物扁蕾的海北站种群进行了3年的传粉生物学研究实验。与花综合征所表明的繁育系统相反,两年的野外观察发现昆虫的访花频率十分低,不去雄并隔离昆虫处理也能产生大量种子,说明这一种群的繁殖主要是依赖于自花传粉。尽管利用种子结实评价的柱头可授性从花开放4 d后开始下降,但随着花的发育进程,雄蕊的伸长能使得花药与柱头完全接触。实验也证明,柱头可授性和花粉活力都超过5 d,说明花药和柱头的接触能够发生自花授粉。扁蕾的这种自花传粉机制应属于典型的延迟自交类型。自花授粉发生在单花花期快要结束前,自交之前仍然保持异交传粉机制,这种延迟自交避免了自交与异交竞争造成的花粉或者种子折损,并为扁蕾在青藏高原极端环境下由于访花昆虫缺乏造成的异交失败提供了繁殖保障。     

天仙子的花部特征及延迟自交机制

通过实验观察和野外控制授粉等方法,对天仙子的自交亲和能力和自交传粉机制进行了研究。结果显示:(1)天仙子的花不完全雌性先熟,开花进程中雄蕊伸长是维持其混合交配系统的重要花部特征。(2)野外控制授粉实验证明天仙子的自交亲和性高,具有主动自交能力,主动自交发生的时间集中在晚花期,与花药和柱头接触的时间吻合。(3)在花粉活力和柱头可授期内,花药与柱头的接触能够发生自花授粉,这种依赖花药与柱头接触发生的自花授粉机制属于典型的延迟自交类型。研究表明,天仙子不仅在花结构上首先选择了适于异交的特征,而且还利用雄蕊伸长成功实现自花授粉,通过异交与延迟自交混合的交配系统为该物种提供了灵活的遗传与繁殖保障。     

核定位信号及其在病毒感染机制中的研究进展

核定位信号介导的蛋白入核是细胞内信号传递网络中核内外物质信息交流的重要一环,绝大多数病毒蛋白进入细胞核均需要核质转运受体识别和结合入核蛋白携带的核定位信号序列.病毒蛋白的入核转运机制在病毒感染过程中起着至关重要的作用,对于病毒的复制、毒力具有重要意义,针对该机制的研究有利于新的抗病毒靶点的发现.本文对核定位信号的分类信...     

中耳手术面神经定位的研究进展

近年来,随着手术显微镜和电钻的问世,中耳手术面神经损伤率大大降低,但即使是非常有经验的医生也不可避免地有损伤面神经的机会,尤其是当患者为再次手术,或合并感染、胆脂瘤等使正常解剖标志改变、模糊或移位,或先天性畸形者,都会增加手术损伤面神经的机会.本文主要是针对中耳手术面神经定位的研究进展做简要的综述.中耳手术面神经的定位主要是依靠中耳面神经的解剖学标志,例如匙突、砧骨短突、水平半规管、二腹肌脊、鼓索神经等.随着影像学的高速发展,特别是高分辨率CT以及CT的多平面重建(MPR)和曲面重建(CPR)等,对面神经的定位有明显的指导意义.同时熟悉面神经的畸形以及面神经监测技术的开展,对面神经的定位也有一定的帮助.了解国际上中耳手术面神经定位的研究进展,对于面神经的定位、降低中耳术后面神经损伤的概率有着十分重要的意义.     

寄生蜂基于嗅觉信号识别的宿主定位及其机制的研究进展

寄生蜂对宿主的成功定位是其繁衍后代的关键步骤之一,主要受挥发性化合物的调节。首先,雌性寄生蜂可根据寄主植物挥发物尤其是植食性昆虫诱导的植物挥发物(herbivore-induced plant volatiles, HIPVs)对宿主的栖息环境进行远距离定位,它们可根据HIPVs提供的信号缩小宿主范围,而HIPVs的混合物极为复杂,其成分和含量受多种因素的调节。尽管如此,萜类是HIPVs中常见的化合物,且被多数行为研究证实在寄生蜂宿主定位中发挥作用。随后,当寄生蜂发现并降落到与宿主相关的植物后,它们可利用宿主衍生的信号近距离定位宿主。宿主的虫体、茧和粪便等释放的挥发性化合物对寄生蜂具有吸引作用,有些宿主粪便的气味可以作为寄生蜂执行宿主定位行为的主信号,而且宿主粪便挥发物的成分因昆虫取食的植物种类的不同而发生变化。此外,来自寄生蜂自身的信息化学物质也有助于同种寄生蜂的其他个体对宿主的定位。寄生蜂对气味分子的感知依赖其主要位于触角上的嗅觉感器,而关于其嗅觉识别的分子机制的研究仍较为薄弱。由于气味结合蛋白(odorant-binding proteins, OBPs)是嗅觉系统中介导气味识别...     

真核生物蛋白质翻译的内部起始机制

蛋白质翻译过程中,翻译的起始步骤是非常重要的．真核生物的翻译起始主要是通过依赖帽子结构的扫描机制进行的．近几年在翻译的研究工作中发现,在一些动物病毒中,蛋白质合成通过一种不同于扫描机制的内部起始机制起始翻译．用内部起始机制翻译的mRNA的5′端非翻译区有一个相对保守的结构,它在内部起始过程中具有重要作用,一些特异的蛋白质因子能够促进在特定位点起始翻译．     

肉牛的数量性状基因座定位研究进展

遗传图谱的发展为寻找和定位影响重要数量性状变异的基因提供了便利。迄今为止,育种学家已经在肉牛的1、2、5、6、14、15、17、18、19、21、23、27、和29号常染色体上发现了QTL的踪迹。候选基因的研分显示肌肉生长抑制素基因等可能就是生长和屠宰重性状的QTL,基困组统计定位则揭示最有可能的QTL区域在2、5、6、15、19、27、29号染色体上。进一步的定位仍需遗传学家、分子生物学家及育种学家的共同努力。     

基于混合遗传算法的偶极子源定位的仿真计算

首先提出一种新的混合遗传算法。在基于实数编码的基础上,通过嵌入一个最速下降算子,结合遗传算法和最速下降法两者的优点,并引入模拟退火的思想,即可改善原算法的局部搜索能力,又能进一步提高优化效率。为了验证算法的可行性,通过对脑电偶极子源定位的仿真计算,证明所提出的新算法与其它优化算法相比,在达到最优解的效率上有了明显的提高。     

The mechanism of low-frequency sound production in muscle.

Frog gastrocnemius muscles stimulated isometrically in a saline bath at 20 degrees C were found to produce a single ringing sound event beginning just before the tension record began to rise. The sound event was substantially over by the time the isometric tension began to fall. Results from studies correlating the spatial pattern of the sound, the amplitude and frequency of the sound as a function of the muscle length, and the response of both the passive and active muscle to a transverse pluck were found to be consistent with the conclusion that the sounds in these muscles are caused primarily by transverse resonant vibrations. As the muscle develops force, its lack of cylindrical symmetry gives rise to lateral motions, which are most likely the initiators of the bending vibrations detected as sound.     

Reassessing mechanisms of low-frequency sound localisation

Interaural time differences (ITDs) are the dominant cues for human localisation of low-frequency sounds. Although a mechanism for ITD processing proposed in 1948 seems applicable to birds, and is consistent with many aspects of the responses found in mammals, recent data suggest that key tenets of the model might need to be reconsidered. The model requires, at every frequency, a distribution of cells with firing rate peaks across all ITD values within the animal's physiological range. The ITD tuning relies on internal delays in the form of a neural delay line. The evidence for such a delay line structure in mammals is not as convincing as it is in birds and, in some small animals the full range of physiological ITDs are not fully represented by peak firing of neurones at every frequency channel. Alternative means of achieving internal delays such as inhibitory inputs or the delays associated with cochlear filtering are being considered.     

Spike-timing-based computation in sound localization

Spike timing is precise in the auditory system and it has been argued that it conveys information about auditory stimuli, in particular about the location of a sound source. However, beyond simple time differences, the way in which neurons might extract this information is unclear and the potential computational advantages are unknown. The computational difficulty of this task for an animal is to locate the source of an unexpected sound from two monaural signals that are highly dependent on the unknown source signal. In neuron models consisting of spectro-temporal filtering and spiking nonlinearity, we found that the binaural structure induced by spatialized sounds is mapped to synchrony patterns that depend on source location rather than on source signal. Location-specific synchrony patterns would then result in the activation of location-specific assemblies of postsynaptic neurons. We designed a spiking neuron model which exploited this principle to locate a variety of sound sources in a virtual acoustic environment using measured human head-related transfer functions. The model was able to accurately estimate the location of previously unknown sounds in both azimuth and elevation (including front/back discrimination) in a known acoustic environment. We found that multiple representations of different acoustic environments could coexist as sets of overlapping neural assemblies which could be associated with spatial locations by Hebbian learning. The model demonstrates the computational relevance of relative spike timing to extract spatial information about sources independently of the source signal.     

Source localization in underwater sound fields

We investigated the acoustical information present in the field of arbitrary sound sources which may provide direction and distance to the source from a local reading of the sound field parameters. If the effects of reflections are negligible, the particle acceleration is directed radially at the instant of sound pressure nulls. The spectral relation between the radial component of the particle aceleration and the sound pressure is characterized by a critical frequency where a sharp transition occurs in the amplitude ratio and the phase relation of these variables. The critical frequency depends on the distance to the source and depends little on the source type (mono-, di- or quadrupole). Thus, a local reading of the particle acceleration and the sound pressure is in principle sufficient to localize the sound source in three dimensions. Fish might use this kind of information for acoustic orientation.     

Neural mechanisms of sound localization in owls

Barn owls localize sound by using the interaural time difference of the horizontal plane and the interaural intensity difference for the vertical plane. The owl's auditory system possesses the two binaural cues in separate pathways in the brainstem. Owls use a process similar to cross-correlation to derive interaural time differences. Convergence of different frequency bands in the inferior colliculus solves the problems of phase-ambiguity which is inherent in cross-correlating periodic signals. The two pathways converge in the external nucleus of the inferior colliculus to give rise to neurons that are selective for combinations of the two cues. These neurons form a map of auditory space. The map projects to the optic tectum to form a bimodal map which, in turn, projects to a motor map for head turning. The visual system calibrates the auditory space map during ontogeny in which acoustic variables change. In addition to this tectal pathway, the forebrain can also control the sound-localizing behaviour.