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.     

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.     

海洋哺乳动物信息素嗅觉的分子进化

研究感觉基因的进化规律是动物进化领域长期探索的重要问题.哺乳动物通常具有2套嗅觉系统:主要嗅觉系统(MOS)和犁鼻器系统(VNS).其中,VNS主要感知动物个体释放的信息素分子,而信息素在动物的生殖和社会行为中起重要调节作用.为了研究动物信息素嗅觉进化的背后推动力,对海洋哺乳动物的代表物种进行了Trpc2基因(VNS功能的分子标记)的序列测定和进化分析.以前的研究表明,Trpc2基因仅在VNS中表达,其序列完整/缺失与VNS的功能完整/退化完全一致.本研究结果显示,鲸类和海牛类的Trpc2为假基因,鳍脚类的1个分支类群(海豹类)和水獭类的Trpc2也是假基因,提示VNS功能丢失,即信息素嗅觉功能退化;而北极熊和鳍脚类的另一个分支类群(海狮类)保留了1个完整的Trpc2,并且这个基因仍受强烈的净化选择和功能限制,提示信息素嗅觉功能仍然保留.进一步分析表明,信息素嗅觉退化的海兽主要在水中交配,而信息素嗅觉保留的海兽主要在陆地上交配.本研究提出了一个新的科学假说:交配场所的选择可能推动了海洋哺乳动物信息素嗅觉的进化.     

昆虫嗅觉中枢系统对外周信号的整合编码研究进展

灵敏、复杂的嗅觉对于昆虫的生存和繁殖至关重要。触角是昆虫主要的嗅觉器官,其表面覆盖着大量各种类型的嗅觉感受器,这些感受器能够感受环境中的挥发性化合物,并将感受到的化学信号转化为电信号。电信号首先经嗅觉受体神经元传递到大脑中的初级嗅觉中枢触角叶,不同来源的信号在此被初步整合加工,再经投射神经元投射到高级神经中枢蘑菇体和侧角叶,蘑菇体主要与后天的气味学习行为有关,而侧角叶主要负责先天的气味行为反应。本文以模式昆虫果蝇和鳞翅目昆虫为主,综述了昆虫嗅觉中枢系统对外周信号整合编码的研究进展。研究人员依靠黑腹果蝇Drosophila melanogaster遗传操作技术的便利在该领域取得了快速进展,系统阐释了初级嗅觉中枢对气味信息的整合与向下传递以及高级嗅觉中枢对这些信息的再次加工。由于遗传操作的限制,其他昆虫与果蝇相比研究进展较慢,目前研究主要局限于对鳞翅目昆虫中枢神经系统的结构解剖和触角叶内各类神经元的记录等。因此,我们建议展开以下研究:(1)利用模式昆虫果蝇,全面解析侧角叶对气味信息的编码,阐明其对各类气味特异行为反应的神经机制;(2)大力发展非模式昆虫的遗传操作技术,结合双光子钙离子成像等...     

非编码RNA与哺乳动物基因组印记的起源

基因组印记是由亲本来源不同而导致等位基因表达差异的一种遗传现象,主要发生在胎盘哺乳动物（真哺乳类）和显花植物中.大部分印记基因都分布在印记基因簇内,其中包含大量的非编码RNA基因.印记基因的表达受印记控制区（ICRs）的顺式调控.基因组印记产生的原因及过程是现代遗传学研究的一个热点问题,分析印记同源区从非印记物种到印记物种的过渡,为解决这一问题提供了重要启示.最近,原始哺乳动物（有袋类和单孔类）模式物种全基因组测序的完成,极大地促进了印记同源区的比较分析研究.本文对这些研究进行了回顾和分析,发现非编码RNA与哺乳动物基因组印记获得关系密切.主要依据为：（1）伴随着基因组印记的获得,印记区有大量的非编码RNA新基因出现;（2）与基因组印记相关的一些保守非编码RNA的表达发生了显著变化.此外,对15种脊椎动物中印记snoRNA基因系统分析的结果表明：印记snoRNA起源于真哺乳类与有袋类动物分化之后,并且在真哺乳类辐射进化之前发生了迅速的扩张,主要的基因家族在这一时期已经形成.这些结果进一步证明了非编码RNA与基因组印记获得的密切联系.非编码RNA可能主要通过调控印记表达和诱导染色体表观遗传修饰两种机制,参与哺乳动物基因组印记的获得.     

腺苷酸环化酶3缺失对小鼠主要嗅觉表皮组织内DNA甲基化的影响

腺苷酸环化酶3 (adenylate cyclaseⅢ,AC3)是嗅觉系统中的重要成分,AC3缺失后小鼠的主要嗅觉表皮组织(main olfactory epidermal,MOE)随年龄增长逐渐变薄,MOE内基因表达谱发生改变. DNA甲基化在动物发育、基因表达调控中具有重要作用.为了探讨AC3缺失后小鼠MOE内基因启动子甲基化水平的改变以及对基因表达的影响,本文采用DNA甲基化免疫共沉淀芯片(methylated DNA immunoprecipitation chip,MeDIP-chip)筛选AC3缺失小鼠MOE内启动子区甲基化差异表达基因,利用甲基化特异PCR (methylation-specific PCR,MSP)、实时荧光定量PCR (qRT-PCR)进一步检测部分甲基化差异基因的DNA甲基化水平改变和表达差异.结果表明,AC3缺失小鼠中有1 978个基因启动子的甲基化水平发生了改变,占总探针数的9%,其中727个基因启动子甲基化水平升高,1 251个甲基化水平降低.功能分析表明,这些启动子甲基化发生改变的基因主要涉及的功能分别与嗅觉受体、神经发育、cAMP信号通路、ATP结合、钙离子调控、乙酰化修饰、转录因子等相关. MSP检测表明,嗅觉受体基因Olfr1153、Olfr231、Olfr378、Olfr651、Olfr691启动子区的甲基化水平升高,Cngb1、Pde4a和Olfr1394基因启动子区的甲基化水平降低. qRT-PCR结果显示,基因Cngb1、Hcn4、Olfm1、Olfr1394、Olfr1153、Olfr231、Olfr378、Olfr691的表达水平显著下降,而Pde4a和Olfr651基因的表达水平显著升高.总之,AC3缺失后MOE内嗅觉受体基因、神经发育相关基因、cAMP信号通路等相关基因启动子甲基化水平发生显著改变,影响核苷酸切除修复、DNA复制、错配修复等信号通路的传导,从而综合调控小鼠MOE内的基因表达数量和水平.     

棕色田鼠和沼泽田鼠雄性社会行为与嗅觉相关脑区性激素受体表达之间的关系

应用行为聚焦取样观察和免疫组织化学相结合的方法 ,比较研究了棕色田鼠 (Microtusmandarinus)(n =15 )和沼泽田鼠 (M .fostis) (n =15 )在同种雄雄交往中的行为差异 ,及在雄雄交往前后雌激素 β受体(ERβ)和雄激素受体 (AR)表达的差异。在 2h的雄雄交往中 ,前 1h棕色田鼠对同性入侵者有较多的攻击和防御行为 ,后 1h攻击行为较少 ,沼泽田鼠前后 1h差异不大 ,整个 2h期间 ,棕色田鼠较沼泽田鼠对同性入侵者有较多的攻击、防御行为 ,较少的非社会行为。经过免疫组织化学检测 ,没有社会交往时棕色田鼠主嗅球系统投射区和犁鼻系统投射区ERβ免疫阳性细胞 (ERβ IRs)明显少于沼泽田鼠 ,且显色淡 ,AR免疫阳性细胞(AR IRs)在两种鼠间差异不大 ,且都明显少于各自的ERβ IRs。 2h交往后 ,棕色田鼠主嗅球投射区和犁鼻系统投射区的ERβ IRs细胞数明显少于交往前 ,AR IRs细胞数明显多于交往前 ;沼泽田鼠交往前与交往后ERβ IRs和AR IRs细胞数均无显著差异 ,且显著多于交往后棕色田鼠ERβ IRs细胞数 ,显著少于交往后棕色田鼠AR IRs细胞数。以上结果表明 :两种田鼠在社会交往中社会行为不同 ;ERβ的减少和AR的增多可能在社会识别及攻击行为中均起一定的作用 ,可能也是引起两种田鼠社会行为发生差异的原因之一     

哺乳类两大嗅觉系统功能的研究进展

近年来对于嗅觉系统的研究已成为动物学研究的热点之一,本文通过对以往关于哺乳类两大嗅觉系统功能的研究进行总结和回顾,对目前犁鼻器系统(VOE-AOB)和主嗅觉系统(MOE-MOB)功能结论上的争议做了初步探讨。通过概括和总结,发现目前对两大嗅觉系统功能还存在争议,其原因可能有以下几点:以前的研究方法上可能有不完善之处;不同的研究采用的物种不同,结论上的争议也许与不同物种间存在种间差异有关;动物的社会经验对研究结论可能也有一定影响。希望通过本文能进一步促进今后此方面的研究。     

蚊子嗅觉系统的最新研究进展

由于蚊子传播疟疾、登革热、黄热病等多种疾病,严重威胁着人类的健康及生活.现有的化学防治手段不但效果不理想,而且导致蚊子抗性增强,环境污染,并危害到其它生物种群.蚊子的行为很大程度上依赖于它们的嗅觉系统,因而根据蚊子的嗅觉系统的研究来利用化学生态手段去防治蚊子成了近期的研究热点.这一方法不但对环境更加友好,而且对蚊子专一性强,避免伤害其它生物.本文根据近期关于蚊子嗅觉系统的研究,尤其针对蚊子气味结合蛋白(odorant binding protein,OBP)、气味受体(odorant receptor,OR)蛋白和驱蚊胺(DEET)的最新研究结果进行了综述.     

蚊虫搜寻吸血寄主和产卵行为的调节因子及相关嗅觉机理

嗅觉在蚊虫的吸血寄主搜寻、产卵和糖源搜寻行为中起决定作用,而在交配行为中的作用并不清楚。本文系统全面地综述了近20年来蚊虫化学生态学和嗅觉识别的分子机理的研究。蚊虫的触角、下颚须和口喙上的嗅觉感器感觉环境中释放的各种挥发性化合物。气味分子与嗅觉气味结合蛋白和气味受体的结合所启动的一系列生化反应产生神经动作电位。蚊虫嗅觉神经元编码气味中化合物的组成、浓度及其暂时瞬间的浓度变化和空间分布。吸血前后神经元的活性在数量和质量上有变化,反映了蚊虫在搜寻吸血寄主和产卵行为上的调节。在吸血寄主搜寻中,人体和动物释放的二氧化碳、乳酸以及其他气味协同引诱蚊虫向目标气味源定向飞行,最后找到吸血寄主。而成熟产卵雌蚊是利用产卵场所释放的腐烂气味寻找适宜的产卵场所,一些蚊虫卵、幼虫或蛹分泌的产卵信息素引诱和刺激雌蚊产卵,并与产卵生境气味起协同作用。植物气味尤其是花香味引诱蚊虫找到蜜源。驱避剂也是直接或间接通过嗅觉起作用,一些驱蚊剂由于阻断嗅觉反应而抑制蚊虫的定向飞行。从植物、动物或人体以及产卵场所释放的气味中有望找到有效的引诱和驱避化合物。对蚊虫嗅觉识别机理的认识将使我们开发出有效的蚊虫诱捕技术,进而应用于种群监测和控制。     

Olfactory regulation of maternal behavior in mammals

In mammals, olfactory cues are extensively used in many aspects of maternal care to ensure the coordination of mother-infant interactions and consequently the normal development of the offspring. Outside the period of parturition and lactation, when the young are not a behavioral priority, olfactory cues play an inhibitory role on maternal responsiveness since in most mammalian species studied so far, nonpregnant females find the odor of young aversive. On the contrary at the time of parturition, a shift in the hedonic value of infantile odors occurs so that the young now become a very potent stimulus and this sensorial processing constitutes an important part of the maternal motivational system. Moreover, infants' odors provide a basis for individual recognition by their mothers and some species (ungulates) have developed highly specialized mechanisms for processing of the infant signals. Perception of the smell of the young also regulates various aspects of maternal behavior. Dodecyl propionate, a compound released by of pup's preputial glands, has been shown to influence anogenital licking behavior, a fundamental pattern of maternal behavior in rodents. While there is no functional specificity of either the main or the accessory olfactory systems in the development of maternal behavior amongst species, it appears that only the main olfactory system is implicated when individual odor discrimination of the young is required. Neural structures, such as the main olfactory bulb, undergo profound changes when exposed to offspring odors at parturition. These changes in synaptic circuitry contribute both to maternal responsiveness to these odors, to their memorization, and to effects of long-term maternal experience.     

棕色田鼠雄性幼体不同发育期犁鼻器和副嗅球的组织结构

通过对出生后不同发育时期雄性棕色田鼠犁鼻器和副嗅球进行组织学观察, 探讨棕色田鼠出生后犁鼻器和副嗅球的发育规律。实验以出生后当天(0 日龄) , 5 日龄, 15 日龄, 25 日龄以及成年棕色田鼠为研究对象,副嗅球采用Pischinger 氏染色法染色, 犁鼻器用H. E. 染色法染色后进行组织学观察。结果显示, 棕色田鼠出生时, 犁鼻器和副嗅球就已具有成体的基本结构, 随着动物个体的发育, 犁鼻上皮逐渐增厚, 犁鼻管变长, 犁鼻上皮中神经元密度增加; 腺体逐渐增大, 犁鼻管腔填充物增多, 犁鼻管背外侧的静脉血管逐日增大, 管腔周围出现越来越多的血管; 副嗅球长宽都增加, 僧帽细胞层和颗粒细胞层逐渐增长, 各层细胞密度变化稍有不同;出生后15 日内, 僧帽细胞层细胞密度增加, 15 日龄以后又开始降低, 25 日龄及成体的僧帽细胞层细胞密度与5日龄的相似; 颗粒细胞层细胞密度持续增高。实验结果提示, 棕色田鼠5 日龄时, 犁鼻器和副嗅球已具有了完整的结构, 到25 日龄时可能达到了功能上的成熟。     

Preliminary Assessment of the Impact of MicroRNA-Mediated Regulation on Coding Sequence Evolution in Mammals

Despite prior claims to the contrary, several lines of evidence suggest that selection acts on synonymous mutations in mammals. What might be the mechanisms for such selection? Here I attempt to quantify the constraints on the evolution of the coding sequence resulting from regulation of mRNA by microRNAs (miRNAs) that antisense-bind to the coding region of mRNAs. I employ a set of genes recently experimentally verified to be the target of a miRNA, all with putative antisense pairing domains within the coding sequence. Although very small (～22 nucleotides), 2 of 13 pairing domains show evidence of significantly slow sequence evolution. This, along with evidence that these genes are regulated by the miRNA under consideration, provides the first good candidate domains for intra-CDS pairing of a miRNA in mammals. When analyzed en masse, the putative pairing domains have a significantly reduced rate of synonymous evolution (～35% lower than null). However, given the size and rarity of pairing domains within the coding sequence, the effects that such constraint has on estimates of the mutation rate are small enough to be ignored (probably less than 1% reduction). The pairing sites also have low K_a values and the selection on the synonymous sites is unlikely to lead to misleading reports of localized high K_a/K_s ratios.     

4种两栖爬行动物嗅器和犁鼻器的显微结构比较

用光镜观察了4种两栖爬行动物嗅器和犁鼻器的组织结构.结果显示,北方山溪鲵(Batrachuperus tibetanus)鼻囊内开始分化出犁鼻器,犁鼻器位于嗅器的腹外侧,但犁鼻器还不发达;隆肛蛙(Feirana quadranus)犁鼻器与嗅器虽然共同位于鼻囊内,但犁鼻器较为发达且其周围有发达的犁鼻腺,犁鼻器通过一细小管道与嗅器相通;秦岭蝮(Gloydius qinlingensis)和菜花烙铁头(Trimeresurus jerdonii)犁鼻腔与鼻腔已经完全分离形成两个独立的囊,而且鼻腔又进一步分化为嗅部与呼吸部.说明犁鼻器从有尾两栖动物开始出现,至无尾两栖类开始分化,到蛇类高度发达且成为一个独立器官.犁鼻器的形成是脊椎动物适应陆地生活的直接结果,是四足动物的特征之一.     

黑斑蛙嗅器和犁鼻器的组化及超微结构特征

嗅感受器主要感知外界环境中化学信号分子.本文采用银染、NADPH-组化染色和电镜技术来观察黑斑侧褶蛙(Petophylax nigromaculatus)的嗅器和犁鼻器的功能差异及细胞组成.银染法可对嗅上皮和犁鼻上皮的细胞进行分类及区分.其中,支持细胞胞核深染成黑色,嗅细胞胞核银染为花斑状.细胞计数显示,犁鼻上皮的嗅神经细胞含量百分比显著高于嗅上皮.组化结果显示,黑斑侧褶蛙嗅上皮和犁鼻上皮对NADPH-d表达模式差异显著,前者表达明显高于后者.电镜结果显示,黑斑侧褶蛙嗅上皮和犁鼻上皮的支持细胞由两种类型的细胞组成,分别为纤毛型和颗粒型支持细胞.     

Sexual incentive motivation, olfactory preference, and activation of the vomeronasal projection pathway by sexually relevant cues in non-copulating and naive male rats

There are some apparently healthy male rats that fail to mate after repeated testing with receptive females. We have previously shown that these "non-copulator (NC)" males show no partner preference for a receptive female when given the opportunity to physically interact with a sexually receptive female or a sexually active male. We also demonstrated that although NC males prefer odors from estrous females to odors from anestrous females, this preference is significantly reduced in comparison to the preference displayed by copulating (C) males. The aim of the present study was to evaluate in NC males sexual incentive motivation, that is, the approach behavior of male rats to either a sexually receptive female or a sexually active male in a test where the subjects can smell, hear, and see the stimulus animal but prevents their physical interaction. In addition, we determined whether NC rats have alterations in their ability to detect odors from conspecifics or odors related to food. In the detection of odors from conspecifics, we determined if these NC males are sexually attracted toward odors from receptive females or sexually active males. For food-related odors, we quantified the time it took the subjects to locate a hidden a piece of apple. Finally, using the induction of Fos-immunoreactivity (Fos-IR) as an index of neuronal activation, we compared the response of the vomeronasal projection pathway (VN pathway) of C and NC male rats exposed to estrous bedding. Males without sexual experience (WSE) were included in all experiments to determine the importance of previous heterosexual experience in the different behavioral tests and in the activity of the VN pathway. In the sexual incentive motivation test, we found that C and WSE male rats have a clear preference for estrous females over sexually active males, whereas NC male rats showed no preference. In odor tests, our results showed that C males had a clear preference for odors from estrous females as opposed to odors from sexually active males. Although NC and WSE male rats showed a preference for estrous female odors, this preference was significantly reduced compared to that shown by C males. No differences were found between WSE, C, and NC males in the detection of stimuli associated with food-related odors. A significant increase in Fos-IR was observed in the mitral cell layer of the accessory olfactory bulb in all groups when exposed to estrous bedding. However, only the C male rats exposed to estrous female bedding showed an increase Fos-IR in all structures of the VN pathway. An increase in Fos-IR was observed in the medial preoptic area (MPOA) of WSE males exposed to estrous bedding. No increases in Fos-IR were detected along the VN pathway in NC male rats. We proposed that NC male rats do not display sexual behavior due to a reduced sexual motivation that could be caused by alterations in the neuronal activity of the VN pathway during the processing of estrous odors.     

Emerging views on the distinct but related roles of the main and accessory olfactory systems in responsiveness to chemosensory signals in mice

In rodents, the nasal cavity contains two separate chemosensory epithelia, the main olfactory epithelium, located in the posterior dorsal aspect of the nasal cavity, and the vomeronasal/accessory olfactory epithelium, located in a capsule in the anterior aspect of the ventral floor of the nasal cavity. Both the main and accessory olfactory systems play a role in detection of biologically relevant odors. The accessory olfactory system has been implicated in response to pheromones, while the main olfactory system is thought to be a general molecular analyzer capable of detecting subtle differences in molecular structure of volatile odorants. However, the role of the two systems in detection of biologically relevant chemical signals appears to be partially overlapping. Thus, while it is clear that the accessory olfactory system is responsive to putative pheromones, the main olfactory system can also respond to some pheromones. Conversely, while the main olfactory system can mediate recognition of differences in genetic makeup by smell, the vomeronasal organ (VNO) also appears to participate in recognition of chemosensory differences between genetically distinct individuals. The most salient feature of our review of the literature is that there are no general rules that allow classification of the accessory olfactory system as a pheromone detector and the main olfactory system as a detector of general odorants. Instead, each behavior must be considered within a specific behavioral context to determine the role of these two chemosensory systems. In each case, one system or the other (or both) participates in a specific behavioral or hormonal response.     

The "male effect" in sheep and goats: a review of the respective roles of the two olfactory systems

In sheep and goats, exposure of seasonally anestrous females to sexually active males results in activation of luteinizing hormone (LH) secretion and synchronized ovulation. This phenomenon is named "the male effect" and seems to constitute a major factor in the control of reproductive events. This effect depends mostly on olfactory cues and is largely mimicked by exposure to male fleece only. In sheep, preventing the vomeronasal organ (VNO) from functioning does not affect the female responses to male odor suggesting that, unlike in rodents, the accessory olfactory system does not play the major role in the perception of this pheromonal cue. Female responses also seem to depend on previous experience, an effect that is not common for pheromones and renders this model of special interest. The aim of the present report is to summarize our current knowledge concerning the "male effect" and in particular to clarify the respective roles of the two olfactory systems in the processes involved in this effect.     

Ex Vivo Preparations of the Intact Vomeronasal Organ and Accessory Olfactory Bulb

The mouse accessory olfactory system (AOS) is a specialized sensory pathway for detecting nonvolatile social odors, pheromones, and kairomones. The first neural circuit in the AOS pathway, called the accessory olfactory bulb (AOB), plays an important role in establishing sex-typical behaviors such as territorial aggression and mating. This small (<1 mm³) circuit possesses the capacity to distinguish unique behavioral states, such as sex, strain, and stress from chemosensory cues in the secretions and excretions of conspecifics. While the compact organization of this system presents unique opportunities for recording from large portions of the circuit simultaneously, investigation of sensory processing in the AOB remains challenging, largely due to its experimentally disadvantageous location in the brain. Here, we demonstrate a multi-stage dissection that removes the intact AOB inside a single hemisphere of the anterior mouse skull, leaving connections to both the peripheral vomeronasal sensory neurons (VSNs) and local neuronal circuitry intact. The procedure exposes the AOB surface to direct visual inspection, facilitating electrophysiological and optical recordings from AOB circuit elements in the absence of anesthetics. Upon inserting a thin cannula into the vomeronasal organ (VNO), which houses the VSNs, one can directly expose the periphery to social odors and pheromones while recording downstream activity in the AOB. This procedure enables controlled inquiries into AOS information processing, which can shed light on mechanisms linking pheromone exposure to changes in behavior.