广义Logistic模型奇摄动问题的渐近分析

本文讨论了一类具有慢变参数的广义Logistic模型的渐近性态.首先,用匹配法构造了其渐近近似解,其次运用上下解法对近似解的一致有效性进行了证明,并给出了近似解与精确解之间的误差估计.最后,通过几个例子将所求近似解与精确解进行了比较,表明了文中方法的有效性.     

鱼类嗅觉系统和性信息素受体的研究进展

鱼类嗅觉系统包括外部嗅觉器官、嗅神经和嗅球三个部分.嗅觉器官也称为嗅囊,由嗅上皮和髓质组成.气味物质的化学信息主要由嗅上皮上随机分布的嗅觉感受神经元感知,通过嗅神经将嗅觉信息传递到嗅球,嗅球在空间上有不同的功能分区,嗅觉信息经过嗅球各分区整合后分别传入端脑,发挥其生理功能.性信息素在鱼类生殖过程中的作用是通过嗅觉系统来完成的,其中嗅觉感受神经元上的性信息素受体起着重要作用.鱼类性信息素受体的研究主要从两个方面入手,一是从低浓度特异的性信息素引起嗅觉器官电生理反应或行为反应入手,寻找特异的性信息素受体;二是参照哺乳动物嗅觉受体的研究结果,从嗅觉受体基因遗传保守性入手,研究鱼类性信息素受体的结构与功能.     

嗅觉功能活动调节豚鼠海马未成熟神经元的发育

目的观察嗅觉功能活动对豚鼠两侧海马齿状回颗粒细胞下层(SGZ)未成熟神经元表达及发育的影响。方法通过电烙铁将2月龄(n=10)和1岁龄(n=10)雄性豚鼠左侧鼻腔内嗅粘膜损伤,然后堵住鼻孔以建立嗅觉剥夺模型。将每组豚鼠编排随机数字表,随机饲养4周(n=5)和8周(n=5)之后灌注取材,采用免疫组织化学技术观察2组豚鼠在2个时间点自身两侧SGZ区微管相关蛋白(doublecortin,DCX)的表达;运用免疫荧光双标染色观察SGZ区DCX+细胞转化为Neu N(成熟神经元标记物)的频率。结果 2月龄豚鼠嗅觉剥夺4周、8周后,1岁龄豚鼠嗅觉剥夺8周后,剥夺侧SGZ区DCX+细胞密度较自身非剥夺侧均显著下降;2月龄和1岁龄豚鼠嗅觉剥夺8周后,两组豚鼠嗅觉剥夺侧SGZ区DCX+细胞与Neu N+细胞共表达的频率显著低于自身未剥夺侧。结论正常的嗅觉功能活动对豚鼠海马未成熟神经元的表达及发育起调节作用。     

带时滞互惠模型的稳定性和行波解的存在性

本文建立了一类空间非局部带时滞影响的互惠生物种群系统模型.前部分利用线性化方法证明了该模型的简单动力学行为,即证明了零平衡点和两个边界平衡点都是不稳定的,唯一的正平衡点是稳定的,同时还用Redlinger上下解方法得出了该模型的初边值问题存在唯一的正则解;后部分则证明了该反应扩散系统连接零平衡点和正平衡点的行波解的存在性.     

哺乳动物主要嗅觉系统和犁鼻系统信息识别的编码模式

哺乳动物具有两套嗅觉系统, 即主要嗅觉系统和犁鼻系统。前者对环境中的大多数挥发性化学物质进行识别, 后者对同种个体释放的信息素进行识别。本文从嗅觉感受器、嗅球、嗅球以上脑区三个水平综述了这两种嗅觉系统对化学信息识别的编码模式。犁鼻器用较窄的调谐识别信息素成分, 不同于嗅上皮用分类性合并受体的方式识别气味; 副嗅球以接受相同受体输入的肾丝球所在区域为单位整合信息, 而主嗅球通过对肾丝球模块的特异性合并编码信息; 在犁鼻系统, 信息素的信号更多地作用于下丘脑区域, 引起特定的行为和神经内分泌反应。而在主要嗅觉系统, 嗅皮层可能采用时间模式编码神经元群, 对气味的最终感受与脑的不同区域有关。犁鼻系统较主要嗅觉系统的编码简单, 可能与其执行的功能较少有关。     

黄胸散白蚁对马缨丹叶片提取物的嗅觉行为反应

[目的]为了明确黄胸散白蚁Reticulitermes flaviceps对马缨丹Lantana camara叶片不同溶剂提取物的嗅觉行为反应。[方法]利用"Y"型嗅觉仪测定了黄胸散白蚁饥饿与否、气流速度、观察时间对其嗅觉行为反应的影响,优化了测定条件;用小滤纸片法和优化条件下"Y"型嗅觉仪测定了马缨丹叶片不同溶剂提(萃)取物对黄胸散白蚁的嗅觉行为反应。[结果]白蚁饥饿12 h,气流速度为2 L/min,10 min后观察为用"Y"型嗅觉仪测定白蚁对提(萃)取物嗅觉行为反应的最优条件。两种测定方法均表明,马缨丹干叶片氯仿提取物、乙醇提取物的乙酸乙酯和石油醚萃取物对黄胸散白蚁均具有驱避作用,随着提(萃)取物浓度的增大驱避作用越强。[结论]马缨丹叶片中含对白蚁具有驱避作用的物质,为白蚁防治提供了新的途径,也为进一步研究提供了科学依据。     

落叶松球果苍蝇对兴安落叶松球果挥发性物质的反应(英文)

兴安落叶松球果挥发性物质中主要为单萜类物质,１９９８年用几种主要的单萜类物质为气味源,利用四臂嗅觉仪对落叶松球果花蝇进行了嗅觉反应试验。结果表明,根据被害球果挥发性物质的自然比例配制的α－蒎烯、β－蒎烯、月桂烯、罗勒烯等４种物质的混合液对球果花蝇表现为诱引作用,而球果花蝇对其它某些气味物质表现为忘避反应。挥发性物质的林间喷洒试验结果与嗅觉反应试验结果一致。讨论了单萜类物质在球果花蝇对寄主定位和产卵过程中的诱引或驱避作用。     

烟夜蛾和棉铃虫对高浓度烟草挥发物的电生理和行为反应

寡食性的烟夜蛾Helicoverpa assulta (Guenée)和广食性的棉铃虫H. armigera (Hübner)是夜蛾属Heliothis的两近缘种昆虫。主要的农作物中,棉花和番茄上极少发现烟夜蛾,而辣椒上几乎没有棉铃虫,只有烟草均为二者所嗜食,也唯独在烟草上它们可以稳定共存。为明确植物挥发物对昆虫寄主定向和选择行为的影响,本文运用触角电位（EAG）和风洞技术,测定了两种夜蛾的处女雌蛾、交配雌蛾及雄蛾对20种高浓度（0.1 mol/L）烟草挥发物的电生理和行为反应。结果表明：烟夜蛾和棉铃虫对测试的烟草挥发物均可产生EAG反应,而且都表现出绿叶气味＞脂类和芳香化合物＞单萜、倍半萜和杂环化合物的总体反应趋势;两种夜蛾对多数化合物的EAG反应既无显著的种内性别差异,也无显著的种间差异,表明二者嗅觉神经系统对寄主气味图谱的识别和感受能力具有一定的相似性,可对寄主植物的化学信息产生相同的“理解”;二者的行为反应结果与EAG反应结果基本一致,即两种夜蛾受到的嗅觉刺激与产生的行为反应具有统一性,结合两种夜蛾寄主范围的差异,推测烟草挥发物主要影响两种夜蛾的寄主定向行为,而寄主选择行为可能更依赖于二者与植物接触后对植物理化性质的评价过程。     

啮齿动物的嗅觉通讯研究进展

通过对近40 年来啮齿动物嗅觉通讯的研究综述, 主要介绍嗅觉信号的来源、组成及其对啮齿动物行为生理所产生的作用。啮齿动物嗅觉通讯的信号来源主要是粪便、尿液和特化皮肤腺等, 对这些化学信号的成分分析主要集中在各种信息素(Pheromone) 的结构、来源及其引起的行为反应。目前, 在对啮齿动物嗅觉通讯神经通路的研究中, 对主嗅觉系统和犁鼻器系统在动物嗅觉通讯中的作用仍将是人们研究的重点; 而通过信息素作用所产生的各种行为反应的神经内分泌机制也是动物嗅觉通讯领域研究的热点之一。研究气味信号对动物行为和生理等方面所产生的作用, 将有助于揭示啮齿动物嗅觉通讯在其社会行为中的重要作用。     

秦岭蝮嗅觉系统和犁鼻系统的显微结构观察

用光镜观察了秦岭蝮Gloydius qinlingensis嗅觉系统和犁鼻系统的组织结构.结果显示秦岭蝮嗅觉系统主要包括嗅器和嗅球,犁鼻系统主要包括犁鼻器和副嗅球,并且嗅器和犁鼻器已经完全分离形成两个独立的囊,犁鼻器位于嗅器的内侧.嗅器粘膜上皮进一步分化为嗅上皮和呼吸上皮,背侧嗅上皮下的固有层内有丰富的Bowmans腺,腹侧呼吸上皮内有大量的杯状细胞,其固有层未见有Bowmans腺.鼻腔的中段出现了发达的犁鼻器,犁鼻上皮明显比嗅上皮厚,其固有层内未见有犁鼻腺,在犁鼻腔内还有蘑菇体.     

Combined behavioral and c-Fos studies elucidate the vital role of sodium for odor detection

Salt, known as taste quality, is generally neglected in olfaction, although the olfactory sensory neurons stretch into the salty nasal mucus covering the olfactory epithelium (OE). Using a psychophysical approach, we directly and functionally demonstrate in the awake rat for a variety of structurally diverse odorants that sodium is a critical factor for olfactory perception and sensitivity, both very important components of mammalian communication and sexual behavior. Bathing the olfactory mucus with an iso-osmotic sodium-free buffer solution results in severe deficits in odorant detection. However, sensitivity returns fully within a few hours, indicating continuous mucus production. In the presence of sodium in the mucus covering the OE, all odorants induce odorant-specific c-Fos expression in the olfactory bulb. Yet, if sodium is absent in the mucus, no c-Fos expression is induced as demonstrated for n-octanal. Our noninvasive approach to induce anosmia in mammals here presented--which is fully reversible within hours--opens new possibilities to study the functions of olfactory communication in awake animals.     

The minimum number of neurons in the central olfactory pathway in relation to its function: a retrograde fiber tracing study.

The present study was aimed at determining the functionally essential size of the neuronal population in the central olfactory nervous system. Using conditioned rats who had learnt to avoid repellent (cycloheximide) solution by olfaction, varying degrees of injuries were made to the lateral olfactory tract, a major central olfactory pathway connecting the olfactory bulb to the olfactory cortex. After examining their olfactory ability to discriminate cycloheximide solution from water, intact bulbar projection neurons (mitral cells) with fiber connections to the olfactory cortex were quantified using a retrograde fiber tracing technique. The numbers of retrogradely labeled mitral cells from the rats with normal olfaction ranged between 20 and 92% of the control value, while those numbers from the anosmic rats ranged between 0 and 22%. We conclude that the functionally essential neuronal population is approximately one-fifth of the total in the central olfactory pathway, a presumed threshold value in terms of the ability to avoid cycloheximide solution by olfactory discrimination.     

Lessons from snail tentacles

The olfactory system of the snail is functionally capable andstructurally complex. The morphology of the olfactory epitheliumand the glomeruli are similar to analogous structures in vertebrates.However, the snail system differs markedly from the vertebratesystem in its lack of a mucus secretion and the apparent absenceof spatial patterning. Such similarities and differences teachus about the limitations and options governing the evolutionof olfactory systems. The comparative approach leads to thefollowing conclusions, or ‘lessons’: (1) Death andreplacement is normal for olfactory receptors. (2) Olfactionrequires large numbers of receptors and other neurons. (3) Glomerularstructures in the olfactory neuropil aid sensory processing.(4) Local interactions are important in the early stages ofolfactory processing. (5) The role of mucus in olfaction ispeculiar to the vertebrate nose. (6) The spatial patterningof odor responses is not necessary for effective odor processing.     

Bovine olfactory and nasal respiratory epithelium surfaces

Summary High-voltage transmission electron microscopy and cryo-ultramicrotomy together with scanning electron microscopy and some conventional transmission electron microscopy of ultrathin sections have been applied to the mucous surfaces of bovine olfactory and respiratory epithelia. Distal segments of olfactory cilia tend to run in parallel and could be followed over distances up to about 30 m using high-voltage electron microscopy. This technique and scanning electron microscopy showed that on average 12–13 of such cilia could be observed per nerve ending. After correction for obscured cilia this number becomes about 17. High-voltage micrographs and micrographs made from sections prepared with a cryo-ultramicrotome showed the presence of electron-lucent pockets inside the olfactory mucus. The latter technique also showed that the mucus itself is not fibrous, but rather a continuum varying in electron density. The mucus layer contains various granular structures. Ciliary and microvillar membranes appear thicker with cryo-ultramicrotomy than when the sections are prepared with conventional techniques. The cores of the axonemal microtubules in olfactory as well as in respiratory cilia are darkly stained with this technique. Vesicles present inside the nerve endings are also darkly stained. Dimensions and some other numerical values of interest in olfaction are presented.     

Olfactory receptor localization and function: an emerging role for GPCR heterodimerization

Research on olfaction has been fraught with considerable frustration because none of the hundreds of olfactory receptors make it to the cell surface on their own when expressed in heterologous systems. Recent work indicates that the heterodimerization of olfactory receptors with beta2-adrenergic receptors results in surface expression of these G protein-coupled receptors. Similar conclusions--that heterodimerization is essential for surface expression of olfactory receptors--have been drawn from research in Drosophila utilizing completely different knockout and functional approaches. Together these findings may unlock the solution to a problem that has plagued the molecular study of olfaction since the cloning of the first olfactory G protein-coupled receptor over twelve years ago.     

Single unit recording from olfactory cilia.

Sensory cilia from olfactory receptor cells can be pulled into a patch pipette located above the mucus layer of an olfactory mucosa. While the pipette does not form a tight electrical seal with the ciliary membrane, it nevertheless allows to record current transients driven by action potentials arising in the olfactory neuron. This method is an alternative to single-unit-recording with electrodes pushed into the mucosa and, in some respects, to patch clamp recordings from isolated olfactory cells. Its advantage is technical simplicity and minimal disturbance of the neuron from which signals are derived. Less than 5% of the chemosensitive apical surface of the neuron is covered by the pipette. The neuron remains in situ and its cilia remain covered with some mucus. (However, mucus is in part dissolved by the bathing solution). Odorant thresholds in the picomolar range were thus obtained.     

fMRI activation in response to odorants orally delivered in aqueous solutions

During food intake flavor perception results from simultaneous stimulation of the gustatory, olfactory and trigeminal systems. Olfactory stimulation occurs mainly through the retronasal pathway and the resulting perception is often interpreted as a taste perception, thus leading to the well-known sensory confusion between taste and olfaction. The present experiment was designed to study, with functional magnetic resonance imaging (fMRI), the cortical representation of olfactory perception in humans in response to retronasal stimulation by odorants delivered in aqueous solution. Psychophysical evaluation confirmed that the stimuli acted as pure olfactory stimuli through the retronasal pathway and did not present any taste component. Results showed activation in all brain regions previously described with neuroimaging techniques using olfactory stimulation with an odorized air flow. Piriform and orbitofrontal cortex were found activated as well as the hippocampal region, the amygdala, the insular lobe, the cingulate gyrus and the cerebellum. These results demonstrate the feasibility of efficiently stimulating the olfactory system in an fMRI scanner through the retronasal pathway with liquids delivered to the oral cavity. The presentation of olfactory stimuli in liquids to the mouth is a realistic model for the study of food-related flavor perception. This stimulation protocol furthermore allows presenting taste and olfactory stimuli separately or combined, thus allowing for direct comparisons between single modality representation, taste or olfaction, and representation of multi-modality mixtures.     

Cortical contributions to olfaction: plasticity and perception

In most sensory systems, the sensory cortex is the place where sensation approaches perception. As described in this review, olfaction is no different. The olfactory system includes both primary and higher order cortical regions. These cortical structures perform computations that take highly analytical afferent input and synthesize it into configural odor objects. Cortical plasticity plays an important role in this synthesis and may underlie olfactory perceptual learning. Olfactory cortex is also involved in odor memory and association of odors with multimodal input and contexts. Finally, the olfactory cortex serves as an important sensory gate, modulating information throughput based on recent experience and behavioral state.     

昆虫非典型嗅觉受体Orco的功能和分子结构研究进展

嗅觉受体是参与昆虫嗅觉识别过程的一类重要蛋白。在昆虫的众多嗅觉受体中, 有一类受体明显不同于其他受体, 被称为Orco。该受体基因在不同昆虫种间高度保守, 且表达广泛。Orco在昆虫嗅觉识别过程中发挥关键作用。采用基因突变或RNAi等技术使Orco基因沉默后, 昆虫会出现严重的嗅觉缺陷, 但Orco本身不与气味配体结合, 它与传统嗅觉受体形成复合体Or-Orco, 促进传统嗅觉受体在神经元树突膜上的定位并维持其稳定性, 提高传统嗅觉受体对气味反应的效率。昆虫嗅觉受体的结构与脊椎动物的G蛋白偶联受体相似, 均有7个跨膜区, 但二者的膜拓扑结构相反, 昆虫嗅觉受体的N末端位于细胞质膜内, C末端在细胞质膜外, Orco与传统嗅觉受体通过保守的C末端区域相互作用形成一种新型的配体门控离子通道--Or-Orco复合体。阐明Orco在昆虫嗅觉识别中的功能机制, 可为开创基于昆虫嗅觉行为干扰的新的害虫防治措施提供基础。