昆虫触角感器类型及其功能研究进展

触角感器是昆虫对环境变化产生行为响应的重要基本结构单元,作为昆虫内部神经系统与外部环境进行信息交流的关键接口,受到广泛关注。由于不同环境压力的作用,长期适应性进化使昆虫触角上着生有不同类型的感器,且执行着差异化的生物学功能。触角感器在昆虫识别寄主、寻找配偶、躲避天敌等行为变化中具有重要作用,若深入理解昆虫行为变化的内在机理,则有必要清晰认识昆虫触角感器类型与潜在功能。本文对已有研究结果进行系统性综述与总结。截止目前,共发现有61种昆虫触角感器类型,且触角感器存在种内与种间特征差异。同时针对12种常见的触角感器功能进行梳理,提出昆虫触角感器未来可深入开展的研究方向。本文全面了解各昆虫触角感器类型特征和功能,为从形态结构方面进行昆虫分类研究提供新视角,也为今后从化学生态学角度深入开展昆虫行为对环境改变的适应性等研究提供科学依据。     

Comparison of male antennal morphology and sensilla physiology for sex pheromone olfactory sensing between sibling moth species: Ectropis grisescens and Ectropis obliqua (Geometridae)

Ectropis grisescens and Ectropis obliqua (Lepidoptera: Geometridae) are sibling pest species that co‐occur on tea plants. The sex pheromone components of both species contain (Z,Z,Z)‐3,6,9‐octadecatriene and (Z,Z)‐3,9‐cis‐6,7‐epoxy‐octadecadiene. E. obliqua has (Z,Z)‐3,9‐cis‐6,7‐epoxy‐nonadecadiene as an additional sex pheromone component, which ensures reproductive segregation between the two species. To ascertain the detection mechanism of olfactory organs for sex pheromone components of E. grisescens and E. obliqua, we applied scanning electron microscopy and single sensillum recording to compare antennal morphology and sensillum physiology in the two species. There was no apparent morphological difference between the antennae of the two species. Both species responded similarly to all three sex pheromone components, including, E. obliqua specific component. The distribution patterns of antennal sensilla trichodea differed between the two species. Sex pheromone olfactory sensing in these sibling species appears to be determined by the density of different types of olfactory sensing neurons. Dose‐dependent responses of sensilla trichodea type 1 to (Z,Z)‐3,9‐cis‐6,7‐epoxy‐octadecadiene, the most abundant component, showed an “all or none” pattern and the other two components showed sigmoidal dose‐response curves with a half threshold of 10^?4 (dilution equal to the concentration of 10 μg/μl). These results suggest that the major sex pheromone component functions as an on–off controller while secondary components function as modulators during olfactory transmission to the primary olfactory center.     

Freeze-fracture characteristics of insect gustatory and olfactory sensilla

Summary Freeze-fracture data on antennal olfactory and labellar gustatory sensilla of the blowfly Calliphora vicina were compared with those of vertebrate olfactory organs.Insect antennal and vertebrate olfactory axons have similar diameters and show vesicular expansions; insect labellar axons are on average twice as thick and show no vesicular expansions. Vertebrate olfactory and insect labellar and antennal axons display similar intramembranous particle densities. Antennal axons show particle arrangements, resembling tight-junctions. The few extremely thick axons found in labella and antennae show particle arrangements resembling gap-junctions.In regions, proximal to the pores in the insect sensillar hairs, P-faces of olfactory and gustatory cilia show about 200 particles/m². The most proximal and distal portions of the sensory cilia, necklaces and regions in the vicinity of the hair pores respectively, were only encountered in antennal sensilla. P-faces of the ciliary membranes underneath these pores display 1,000–1,200 particles/ m² in unbranched and branched cilia. These values agree with values found in vertebrate olfactory cilia. It is suggested that these high particle densities are related to entities involved in chemoreceptive activities.Accessory cell micropliae have P-face densities of 2,000–3,000 particles/ m², values similar to those found in vertebrate supportive cell microvilli. The membranes of the accessory cells display septate-junctions in areas where these cells overlap themselves, each other and in places where they adhere to the exoskeleton or the basement membrane.     

Morphogenesis of the antenna of the male silkmoth. Antheraea polyphemus, III. Development of olfactory sensilla and the properties of hair-forming cells

During adult development of the male silkmoth Antheraea polyphemus, the anlagen of olfactory sensilla arise within the first 2 days post-apolysis in the antennal epidermis (stage 1-3). Approximately on the second day, the primary dendrites as well as the axons grow out from the sensory neurons (stage 4). The trichogen cells start to grow apical processes approximately on the third day, and these hair-forming 'sprouts' reach their definite length around the ninth day (stages 5-6). Then the secretion of cuticle begins, the cuticulin layer having formed on day 10 (stage 7a). The primary dendrites are shed, the inner dendritic segments as well as the thecogen cells retract from the prospective hair bases, and the inner tormogen cells degenerate around days 10/11 (stage 7b). The hair shafts of the basiconic sensilla are completed around days 12/13 (stage 7c), and those of the trichoid sensilla around days 14/15 (stage 7d). The trichogen sprouts retract from the hairs after having finished cuticle formation, and the outer dendritic segments grow out into the hairs: in the basiconic sensilla directly through, and in the trichoid sensilla alongside, the sprouts. The trichogen sprouts contain numerous parallel-running microtubules. Besides their cytoskeletal function, these are most probably involved in the transport of membrane vesicles. During the phase of cuticle deposition, large numbers of vesicles are transported anterogradely from the cell bodies into the sprouts, where they fuse with the apical cell membrane and release their electron-dense contents (most probably cuticle precursors) to the outside. As the cuticle grows in thickness, the surface area of the sprouts is reduced by endocytosis of coated vesicles. When finally the sprouts retract from the completed hairs, the number of endocytotic vesicles is further increased and numerous membrane cisterns seem to be transported retrogradely along the microtubules to the cell bodies. Here the membrane material will most probably be used again in the formation of the sensillum lymph cavities. Thus, the trichogen cells are characterized by an intensive membrane recycling. The sensillum lymph cavities develop between days 16-20 (stage 8), mainly via apical invaginations of the trichogen cells. The imago emerges on day 21.     

Contacts of pore tubules and sensory dendrites in antennal chemosensilla of a silkmoth: Demonstration of a possible pathway for olfactory molecules

Antennal olfactory hairs of Antheraea polyphemus were investigated by means of transmission electron microscopy. Adequate preservation of dendrites and extracellular pore tubules is obtained by mechanical opening of the hair lumen and subsequent chemical fixation. The dendritic membrane has a cell coat. The dendrites contain microfilamentous structures in addition to their cytoplasmatic microtubules. The extracellular pore tubules traverse the hair cuticle and reach into the hair lumen for maximally 350 nm. Their diameter varies between 20 and 40 nm, depending on the preparation method. They consist of an electron-dense wall and an electron-lucent core. The wall has a helical substructure and is covered with a fuzzy coat. Contacts of pore tubules and dendritic membranes occur wherever dendrites are near the inner surface of the hair cuticle. Some of the pore tubules terminate approximately at right angles on the dendritic membrane, others lie against the membrane. The contact seems to be made via the surface coats of the tubules and the membrane. The structure of pore tubules which had been negatively stained with uranyl acetate is similar to the conventionally thin-sectioned material. The observations provide support for earlier assumptions that pore tubules are the pathways by which odor molecules reach the dendritic membrane.     

Neuronal degeneration and regeneration induced by axotomy in the olfactory epithelium of Xenopus laevis

The olfactory epithelium (OE) has the remarkable capability to constantly replace olfactory receptor neurons (ORNs) due to the presence of neural stem cells (NSCs). For this reason, the OE provides an excellent model to study neurogenesis and neuronal differentiation. In the present work, we induced neuronal degeneration in the OE of Xenopus laevis larvae by bilateral axotomy of the olfactory nerves. We found that axotomy induces specific‐ neuronal death through apoptosis between 24 and 48h post‐injury. In concordance, there was a progressive decrease of the mature‐ORN marker OMP until it was completely absent 72h post‐injury. On the other hand, neurogenesis was evident 48h post‐injury by an increase in the number of proliferating basal cells as well as NCAM‐180– GAP‐43+ immature neurons. Mature ORNs were replenished 21 days post‐injury and the olfactory function was partially recovered, indicating that new ORNs were integrated into the olfactory bulb glomeruli. Throughout the regenerative process no changes in the expression pattern of the neurotrophin Brain Derivate Neurotrophic Factor were observed. Taken together, this work provides a sequential analysis of the neurodegenerative and subsequent regenerative processes that take place in the OE following axotomy. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 77: 1308–1320, 2017     

Neuroethology of olfactory preference development

Young mammals come to approach the odor of their mother, a response that facilitates their survival during early life. Young rats induce a cascade of events in their mother to induce the emission of her odor. The pups increase circulating prolactin levels, which increases food intake and the emission of large quantities of cecotrophe containing the maternal odor. This odor is synthesized by the action of cecal microorganisms and changes with maternal diet. The diet-dependence of the odor requires the pups to acquire their attraction to the odor postnatally. The acquisition of this preference occurs when an odor is paired with the tactile stimulation that pups receive during maternal care. The action of the tactile stimulation appears to be mediated by noradrenaline. The development of this type of olfactory attraction is accompanied by changes in the regions of the olfactory bulb that are responsive to the attractive odor. Metabolic, anatomical, and neurophysiological changes in response to the attractive odor emerge in such regions of the bulb after early olfactory preference training. © 1992 John Wiley & Sons, Inc.     

Surface coats of pore tubules and olfactory sensory dendrites of a silkmoth revealed by cationic markers

Negatively charged surface coats have been demonstrated on the pore tubules and dendritic membranes of olfactory hairs of male Antheraea polyphemus silkmoths by application of the cationic markers lanthanum (La3+), ruthenium red (RR), and cationized ferritin (CF). Lanthanum and RR diffused readily into the apically opened hairs, whereas CF penetrated only for a relatively short distance. Deposits of the markers are distributed as follows: the inner surfaces of the hair walls are stained by RR and to a small degree by CF; the surfaces of the pore tubules and the dendritic membranes are stained by all three markers. The pore tubules have the strongest affinity for CF. The number of pore tubule-membrane contacts seems to be increased by the cationic dyes. The dendrites are often penetrated by RR, which forms deposits on the inner membrane leaflets, the cytoplasmic microtubules, and microfilaments, and by La3+, but never by CF. The observations provide support for the assumption that, first, the pore tubule-membrane contacts are formed via surface coats of both structures, possibly influenced by cations and, second, that the dendrites remain intact after pinching off the hair tips.     

Very tight contact of tormogen cell membrane and sensillum cuticle: ultrastructural basis for high electrical resistance between receptor-lymph and subcuticular spaces in silkmoth olfactory hairs

A very tight contact is present between the apical membrane of the tormogen cell and the cuticle of the hair base in olfactory sensilla trichodea of Antheraea polyphemus. The contact zone is characterized by numerous hemidesmosome-like structures of the cell membrane, which closely attach the latter to the cuticle. If apically opened hairs are incubated in a LaCl3 solution, the tracer ions do not penetrate the contact zone. It is concluded that the tight contacts are the morphological correlates of the electrical isolation of the receptor-lymph space (cf. de Kramer et al., in press).     

Ultrastructure and early development of the pore plate sensilla ofGymnomerus laevipes (Shuckard) (Vespoidea,Eumenidae)

Summary The oval pore plates (approx. 17 m long) are separated from the antennal cuticle by a furrow, the inner wall of which is flexible. The thin perforated plates are strengthened by an encircling and a middle ledge, the latter of which branches into about 100 almost parallel rims. Each pore plate is innervated by about 20 sense cells. The dendrites fork into numerous branches occupying the outer receptor lymph cavity below the perforated plate. Each pore plate is associated with one thecogen cell, two trichogen cells, one tormogen cell and one envelope cell 4. A so-called additional cell surrounds the sensillum in the imaginal stage. The envelope cells in the later of the two pupal stages examined, have reached an arrangement which immediately precedes the secretion of the cuticulin layer. The surface of the duplicate trichogen cells is almost equal in area to the completed perforated plate. A dendritic sheath, entirely reduced in the imago, protrudes into the exuvial space, where it encloses a single dendrite.In the younger pupal stage the Sensillenanlage forms a crater, whereby envelope cell 4 overtops the other envelope cells. The distal ends of the trichogen cells are divided into several appendages that form the bottom of the crater.     

Sonic hedgehog expression during early tooth development in Suncus murinus

Tooth development is a highly organized process characterized by reciprocal interactions between epithelium and mesenchyme. However, the expression patterns and functions of molecules involved in mouse tooth development are unclear from the viewpoint of explaining human dental malformations and anomalies. Here, we show the expression of sonic hedgehog (Shh), a potent initiator of morphogenesis, during the early stages of tooth development in Suncus murinus. Initially, symmetrical, elongated expression of suncus Shh (sShh) was observed in the thin layer of dental epithelial cells along the mesial-distal axis of both jaws. As the dental epithelium continued to develop, sShh was strictly restricted to the predicted leading parts of the growing, invaginating epithelium corresponding to tooth primordia and enamel knots. We propose that some aspects of Shh function in tooth development are widely conserved in mammalian phylogeny.     

Differentiation of human olfactory system-derived stem cells into dopaminergic neuron-like cells: A comparison between olfactory bulb and mucosa as two sources of stem cells

Cell transplantation has become a possible therapeutic approach in the treatment of neurodegenerative diseases of the nervous system by replacing lost cells. The current study aimed to make a comparison between the differentiation capacity of the olfactory bulb neural stem cells (OB-NSCs) and olfactory ectomesenchymal stem cells (OE-MSCs) into dopaminergic-like neurons under the inductive effect of transforming growth factor β (TGF-β). After culturing and treating with TGF-β, the differentiation capacities of both types of stem cells into dopaminergic neuron-like cells were evaluated. Quantitative real-time polymerase chain reaction analysis 3 weeks after induction demonstrated that the mRNA expression of the dopaminergic activity markers tyrosine hydroxylase (TH), dopamine transporter (DAT), paired box gene 2 (PAX2), and PAX5 in the neuron-like cells derived from OB-NSCs was significantly higher than those derived from OE-MSCs. These findings were further supported by the immunocytochemistry staining showing that the expression of the tyrosine hydroxylase, DAT, PAX2, and paired like homeodomain 3 seemed to be slightly higher in OB-NSCs compared with OE-MSCs. Despite the lower differentiation capacity of OE-MSCs, other considerations such as a noninvasive and easier harvesting process, faster proliferation attributes, longer life span, autologous transplantability, and also the easier and inexpensive cultural process of the OE-MSCs, cumulatively make these cells the more appropriate alternative in the case of autologous transplantation during the treatment process of neurodegenerative disorders like Parkinson's disease.     

动物细胞培养过程中的细胞凋亡

细胞培养过程中的细胞凋亡是细胞受环境因素的影响而发生的现象。随着对细胞凋亡的分子生物学和细胞生物学了解的深入,显示了有效地控制动物细胞培养中细胞凋亡的巨大潜力。包括采用ＤＮＡ重组技术把抗细胞凋亡的基因导入细胞和在培基中加入具有抗细胞凋亡的生存因子或化合物等手段已用于控制细胞培养过程中的细胞凋亡。这些技术将大大延长细胞达到饱和密度后的培养时间,提高细胞培养系统的生产效率。     

A unique cell population in the mouse olfactory bulb displays nuclear beta-catenin signaling during development and olfactory sensory neuron regeneration

Olfactory sensory neurons (OSNs) in the nose form precise connections with neurons in the brain. However, mechanisms that account for the formation of such precise neuronal connections are incompletely understood. Recent studies implicate the function of Wnt growth factors in the formation of neuronal connections. To assess the role of Wnt signaling in the olfactory system, we examined the expression of beta-galactosidase (beta-gal) in the TOPGAL mouse, a transgenic strain in which beta-gal expression reports the activation of the canonical Wnt signaling pathway. In the olfactory epithelium, no beta-gal expression was observed at any developmental stages. In the olfactory bulb (OB), beta-gal expression was observed in a population of cells located at the interface of the olfactory nerve layer and the glomerular layer. The beta-gal expression was developmentally regulated with the peak expression occurring at late embryonic and early postnatal stages and a greatly reduced expression in adulthood. Further, forced OSN regeneration and subsequent reinnervation of the OB led to a reactivation of beta-gal expression in mature animals. The temporal coincidence between the peak of beta-gal expression and formation of OSN connections, together with the spatial localization of these cells, suggests a potential role of these cells and canonical Wnt signaling in the formation of OSN connections in the OB during development and regeneration.     

Ontogeny of pituitary cell-types and the hypothalamo-hypophysial relationship during early development of chum salmon,Oncorhynchus keta

Tissue non-specific alkaline phosphatase is a membrane-bound glycoprotein enzyme which is characterized by its phosphohydrolytic, protein phosphatase, and phosphotransferase activities. This enzyme is distributed virtually in all mammalian tissues, particularly during embryonic development. Its expression is stagespecific and can be demonstrated in the developing embryo as early as the 2-cell stage. It has been suggested that tissue non-specific alkaline phosphatase might play a role in tissue formation. In the study reported here, a genetransfer approach was employed to investigate possible roles for this enzyme by inserting the cDNA for rat tissue non-specific alkaline phosphatase into CHO and LLC-PK1 cells. Permanently transfected cell-lines expressing varying levels of alkaline phosphatase were estblished. The data showed that functional enzyme was expressed in the transfected cells. Cell spreading and attachment were enhanced in transfected CHO cells expressing high levels of tissue non-specific alkaline phosphatase but not in the LLC-PK1 cells. Further, in CHO cells, proliferation was shown to be inversely proportional to the level of the tissue non-specific alkaline phosphatase expression. Homotypic cell association was demonstrated in both alkaline phosphatase-positive and alkaline phosphatase-negative cells in both CHO and LLC-PK1 celllines. Taken together, these findings suggest that in addition to a role in mineralization of bone, tissue nonspecific alkaline phosphatase might also play a role in other cell activities, including those related to differentiation, such as cell-cell or cell-substrate interaction and proliferation.     

Glomerular targets of Heliothis subflexa male olfactory receptor neurons housed within long trichoid sensilla

We used single-sensillum recordings to characterize male Heliothis subflexa antennal olfactory receptor neuron physiology in response to compounds related to their sex pheromone. The recordings were then followed by cobalt staining in order to trace the neurons' axons to their glomerular destinations in the antennal lobe. Receptor neurons responding to the major pheromone component, (Z)-11-hexadecenal, in the first type of sensillum, type-A, projected axons to the cumulus of the macroglomerular complex (MGC). In approximately 40% of the type-A sensilla, a colocalized receptor neuron was stained that projected consistently to the posterior complex 1 (PCx1), a specific glomerulus in an 8-glomerulus complex that we call the Posterior Complex (PCx). We found that receptor neurons residing in type-B sensilla and responding to a secondary pheromone component, (Z)-9-hexadecenal, send their axons to the dorsal medial glomerulus of the MGC. As in the type-A sensilla, we found a cocompartmentalized neuron within type-B sensilla that sends its axon to a different glomerulus of the PCx4. One neuron in type-C sensilla tuned to a third pheromone component, (Z)-11-hexadecenol, and a colocalized neuron responding to (Z)-11-hexadecenyl acetate projected their axons to the anteromedial and ventromedial glomeruli of the MGC, respectively.     

Development of antennal sensilla during moulting inNeomysis integer (Leach) (Crustacea,Mysidacea)

Summary The sensilla are associated with 6 enveloping cells. The innermost enveloping cell (e 1) secretes the dendritic sheath (=thecogen cell). All other enveloping cells are involved in the formation of the outer cuticular apparatus in secreting the cuticle of a definite region of the new hair shaft.The development of the new sensilla begins when an exuvial space expands between old cuticle and epithelium. The newly forming hair shafts lie folded back in an invagination of the epidermal tissue. Only a distal shaft part projects into the free exuvial space. The cuticle of the distal and middle shaft region is secreted by the three middle enveloping cells (e 2–e 4) (=trichogen cells), which are arranged around the dendritic sheath.The wall of the cylinder, in which the distal shaft is situated, is formed by the cuticle of the future proximal shaft region. It is secreted by the outer enveloping cells (e 5 and e 6). Furthermore, both enveloping cells form the hair socket (=trichogen-tormogen cells).The outer dendritic segments encased within a dendritic sheath run up through the newly formed hair shaft and continue to the old cuticular apparatus. The connection between sensory cells and old hair shaft is maintained until ecdysis. On ecdysis the old cuticle is shed and the newly formed shaft of the sensillum is everted like the invaginated finger of a glove. The dendritic sheath and the outer dendritic segments break off at the tip of the new hair shaft. Morphologically this moulting process ensures that the sensitivity of the receptors is maintained until ecdysis.The internal organization of the sensory cells shows no striking changes during the moulting cycle. An increased number of vesicles is accumulated distally within the inner dendritic segments and distributed throughout the outer segments of the dendrites. The cytoplasmic feature of the enveloping cells indicates that synthesis and release of substances for the cuticular apparatus of the new sensillum take place.     

Cell death in development: shaping the embryo

Cell death in animals is normally classified as type I (apoptotic), type II (autophagic) or necrotic. Of the biologically controlled types of death, in most embryos apoptosis is the most common, although in metamorphosis and in cells with massive cytoplasm type II is often seen, and intermediate forms are seen. For vertebrate embryos other than mammals, apoptosis is not seen prior to gastrulation but thereafter is used to sculpt the organs of the embryo, while overproduction of cells with subsequent death of excess cells is a common means of generating high specificity with low information cost. In zebrafish at least, the inability of embryos prior to the maternal-zygotic transition to undergo apoptosis appears to derive from the inability of the cells to resist lysis once apoptosis begins, rather than any inhibition of apoptosis. In mammalian embryos, apoptosis is seen during cavitation. Thereafter, as in other embryos, cell death plays a major role in shaping and sculpting the embryo. In those situations that have been carefully studied, cell death is under tight genetic control (including regulation of gene products whose function in cell death is not yet known, such as cdk5), with activation of apoptosis sometimes regulated by local environmental variables.