昆虫嗅觉系统结构与功能研究进展

昆虫的脑由前脑、中脑和后脑组成,其中前脑含有高级感觉中枢,如蘑菇体和中央复合体,控制昆虫的学习、记忆和运动等高级神经活动;中脑包含触角叶,是嗅觉神经中心;而后脑则通常不发达,主要包括内分泌神经元和控制进食与消化的运动神经元。不同于其他物种,昆虫由于其特殊的生活习性,听觉和视觉系统相对退化,主要依赖嗅觉来捕食、交流和求偶,因此嗅觉系统尤其发达。本文综述了目前对昆虫的脑部主要神经结构和功能(中央复合体、蕈形体和触角叶结构)以及昆虫脑部结构遗传变异(性别异构,不同发育时期、不同昆虫以及昆虫与其他动物的脑部结构差异)的研究进展,并总结了目前昆虫脑对信号的加工处理和识别机制的研究结果。     

The urbilaterian brain: developmental insights into the evolutionary origin of the brain in insects and vertebrates

Classical phylogenetic, neuroanatomical and neuroembryological studies propose an independent evolutionary origin of the brains of insects and vertebrates. Contrasting with this, data from three sets of molecular and genetic analyses indicate that the developmental program of brains of insects and vertebrates might be highly conserved and suggest a monophyletic origin of the brain of protostomes and deuterostomes. First, recent results of molecular phylogeny imply that none of the currently living animals correspond to evolutionary intermediates between protostomes and deuterostomes, thus making it impossible to infer the morphological organization of an ancestral bilaterian brain from living specimens. Second, recent molecular genetic evidence provides support for the body axis inversion hypothesis, which implies that a dorsoventral inversion of the body axis occurred in protostomes versus deuterostomes, leading to the inverted location of neurogenic regions in these animal groups. Third, recent developmental genetic analyses are uncovering the existence of structurally and functionally homologous genes that have comparable and interchangeable functions in early brain development in insect and vertebrate model systems. Thus, development of the anteriormost part of the embryonic brain in both insects and vertebrates depends upon the otd/Otx and ems/Emx genes; development of the posterior part of the embryonic brain in both insects and vertebrates involves homologous control genes of the Hox cluster. These findings, which demonstrate the conserved expression and function of key patterning genes involved in embryonic brain development in insects and vertebrates support the hypothesis that the brains of protostomes and deuterostomes are of monophyletic, urbilaterian origin.     

Induction of supernumerary moults in Galleria mellonella: Evidence for an allatotropic function of the brain

Implantation of brains from chilled Galleria larvae into first-day last-instar host larvae results in a higher incidence of extra-larval moults than in control animals receiving unchilled brains. The ability of the implanted brains to induce an extra-larval moult depends on the number of implanted brains, age of larvae at chilling and the time interval between cooling and removal of the brain. The implanted brains must be present in the host larva for at least 2 days in order to induce an extra-larval moult. The brain taken from a chilled larva has no effect on the activity of the host brain. Application of fluoromevalonate (FMev) to insects which received the brains taken from chilled larvae suppresses the extra-larval moult responses, while implantation of brains from chilled larvae treated with FMev has no effect on the incidence of extra-larval moults produced by the recipients. The possibility that the chilled brain of Galleria larvae produces a hormonal factor that regulates corpora allata activity (allatotropin) is discussed.     

Immunohistochemical evidence for the presence of tryptophan hydroxylase in the brains of insects as revealed by sheep anti-tryptophan hydroxylase polyclonal antibody

Immediately following the discovery of tryptophan hydroxylase in Drosophila, we demonstrated the presence of tryptophan hydroxylase in the brain of the beetle Harmonia axyridis (Coleoptera: Coccinellidae). However, whether tryptophan hydroxylase is present in the brains of other insects is still a matter of discussion. In the current study, sheep anti-tryptophan hydroxylase polyclonal antibody has been applied to test for tryptophan hydroxylase immunoreactivity in a broader taxonomic range of insect brains, including holometabolous and hemimetabolous insects: one species each of Coleoptera, Hymenoptera, Diptera, and Blattaria, and two species of Lepidoptera. All species show consistent tryptophan hydroxylase immunoreactivity with distribution patterns matching that of serotonin. The immuno-positive results of such an antibody in brains from diverse orders of insects suggest that specific tryptophan hydroxylase responsible for central serotonin synthesis is probably present in the brains of all insects. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. This work was supported by grants from the National Natural Science Foundation of China (grant no. 30470546) and the Natural Science Foundation of Jilin Province (grant no. 20030550–7).     

Common ground plans in early brain development in mice and flies

Comparing expression patterns of orthologous genes between insects and vertebrates, we have recently proposed that the ventral nerve cord in insects may correspond to the dorsal nerve cord in vertebrates. Here we show that the early development of the insect and vertebrate brain anlagen is indeed very similar. Insect and vertebrate brains express similar sets of genes in comparable areas with similar functions in the adult. In addition, early axogenesis establishes surprisingly similar patterns of axonal connectivity in both groups. We therefore propose that insect and vertebrate brains are built according to a common ground plan, and that specific areas of the insect and vertebrate brains be considered as homologous, meaning that these areas already existed, with their specific functions, in their common ancestor.     

Cholesterol-reducing bacterium from human feces.

An anaerobic, gram-positive diplobacillus that reduces cholesterol to coprostanol was isolated from human feces and rat cecal contents. The isolates closely resemble a cholesterol-reducing organism isolated by Eyssen et al. (H. Eyssen et al., Eur. J. Biochem. 36:412-421, 1973) from a rat's cecum. These organisms would not form colonies and were isolated and cultivated in an anaerobic medium containing homogenized pork brains (naturally high in cholesterol). These organisms require free or esterified cholesterol for growth. They were isolated by serially diluting feces or cecal contents and inoculating brain medium. Colony-forming organisms, which did not reduce cholesterol, were eliminated by addition of inhibitory agents to the brain medium cultures. This serial dilution procedure was performed until a pure culture of a cholesterol-reducing organism was obtained.     

Cholesterol-reducing bacterium from human feces.

An anaerobic, gram-positive diplobacillus that reduces cholesterol to coprostanol was isolated from human feces and rat cecal contents. The isolates closely resemble a cholesterol-reducing organism isolated by Eyssen et al. (H. Eyssen et al., Eur. J. Biochem. 36:412-421, 1973) from a rat's cecum. These organisms would not form colonies and were isolated and cultivated in an anaerobic medium containing homogenized pork brains (naturally high in cholesterol). These organisms require free or esterified cholesterol for growth. They were isolated by serially diluting feces or cecal contents and inoculating brain medium. Colony-forming organisms, which did not reduce cholesterol, were eliminated by addition of inhibitory agents to the brain medium cultures. This serial dilution procedure was performed until a pure culture of a cholesterol-reducing organism was obtained.     

Brain organization and the origin of insects: an assessment

Within the Arthropoda, morphologies of neurons, the organization of neurons within neuropils and the occurrence of neuropils can be highly conserved and provide robust characters for phylogenetic analyses. The present paper reviews some features of insect and crustacean brains that speak against an entomostracan origin of the insects, contrary to received opinion. Neural organization in brain centres, comprising olfactory pathways, optic lobes and a central neuropil that is thought to play a cardinal role in multi-joint movement, support affinities between insects and malacostracan crustaceans.     

水生昆虫对汞的吸收、富集和水-陆转移

汞是一种人体非必需且有毒的重金属元素,全球性的汞污染因对人类健康具有损害而备受社会关注。自然界中的汞绝大部分会通过江河径流和雨雪尘土的沉降而进入水生生态系统,每年进入水生生态系统的汞至少有10 000吨。水生昆虫作为重要的消费者生物存在于水生生态食物网中,是其重要的组成部分,在水生生态系统的物质循环中扮演着重要角色。本文介绍了近年来水生昆虫与汞之间的相关研究,重点总结了水生昆虫对汞的吸收和富集程度,分析了水生昆虫在汞的水-陆转移中的作用。研究数据表明,水生昆虫对汞的吸收程度与环境因素有关,并通过不同的途径转移到陆地生态系统中,对陆地生态系统上层食物链的生物存在一定的威胁,同时也需注意在对水生昆虫进行开发利用的同时,考虑汞是否超标的因素。     

应用TaqMan定量方法研究巴马香猪CYP1A1、2A19、2E1 mRNA表达

目的巴马香猪是我国具有特色和优势的实验用小型猪资源品系,用于药物评价具有广阔前景。方法 以β-actin作校正,利用TaqMan定量技术对巴马香猪肝、肾、肾上腺、小肠、皮肤、脑、肺、睾丸、前列腺、子宫和卵巢等组织中CYP1A1、2A19和2E1 mRNA的表达水平进行检测,检测结果与报道的人体对应酶CYP1A2、2A6、2E1进行比较。结果巴马香猪CYP1A1、2A19、2E1 mRNA均以肝脏中最高,肝外组织明显较低,并且巴马香猪肝脏CYP1A1、2A19、2E1 mRNA均低于报道的人肝对应酶。结论巴马香猪CYP1A1、2A19、2E1与人体对应酶CYP1A2、2A6、2E1的mRNA组织表达存在一定差异,提示在其作为相应CYP亚型代谢的药物评价时应考虑这种种属差异对实验结果推广到人的影响。     

Conceptual learning by miniature brains

Concepts act as a cornerstone of human cognition. Humans and non-human primates learn conceptual relationships such as ‘same’, ‘different’, ‘larger than’, ‘better than’, among others. In all cases, the relationships have to be encoded by the brain independently of the physical nature of objects linked by the relation. Consequently, concepts are associated with high levels of cognitive sophistication and are not expected in an insect brain. Yet, various works have shown that the miniature brain of honeybees rapidly learns conceptual relationships involving visual stimuli. Concepts such as ‘same’, ‘different’, ‘above/below of’ or ‘left/right are well mastered by bees. We review here evidence about concept learning in honeybees and discuss both its potential adaptive advantage and its possible neural substrates. The results reviewed here challenge the traditional view attributing supremacy to larger brains when it comes to the elaboration of concepts and have wide implications for understanding how brains can form conceptual relations.     

The organization and evolutionary implications of neuropils and their neurons in the brain of the onychophoran Euperipatoides rowelli

This account describes the organization of the brain of the adult Euperipatoides rowelli, a member of the Onychophora or "velvet worms." The present account identifies three cerebral divisions, the first of which contains primary olfactory neuropils, visual neuropils, and brain regions that correspond anatomically to the mushroom bodies of annelids, chelicerates, myriapods, and insects. In common with the brains of many chelicerates, the onychophoran brain is supplied by many thousands of uniformly small basophilic perikarya. Other chelicerate-like features include mushroom body lobes that extend across the brain's midline, an unpaired arch-shaped midline neuropil, and visual pathways that supply midline neuropil and that of the mushroom bodies. These and other similarities with chelicerate brains are discussed in the context of arthropod evolution and with reference to recent molecular phylogenies.     

Identification and characterization of an Egr ortholog as a neural immediate early gene in the European honeybee (Apis mellifera L.)

To date, there are only few reports of immediate early genes (IEGs) available in insects. Aiming at identifying a conserved IEG in insects, we characterized an Egr homolog of the honeybee (AmEgr: Apis mellifera Egr). AmEgr was transiently induced in whole worker brains after seizure induction. In situ hybridization for AmEgr indicated that neural activity of a certain mushroom body (a higher brain center) neuron subtype, which is the same as that we previously identified using another non-coding IEG, termed kakusei, is more enhanced in forager brains. These findings suggest that Egr can be utilized as an IEG in insects.     

Induction of Sarcophaga central nervous system remodeling by 20-hydroxyecdysone in vitro

Proliferation and apoptosis of neural cells were found to be induced simultaneously when larval brains of Sarcophaga peregrina were cultured in the presence of 20-hydroxyecdysone (20-HE) for 24 h. The locations of proliferating cells and apoptotic cells in the brain hemispheres were different. The morphology of brains exposed to 20-HE for a short period proceeded to change sequentially when culture was continued for 2 days even in the absence of 20-HE. These changes mainly consisted of enlargement of the brain hemispheres and extension of the interval between two hemispheres, which closely paralleled the morphological changes of brains that occur in the early pupal stage, suggesting that ecdysteroid alone is sufficient to induce the remodeling of the central nervous system of holometabolous insects. Synthesis of a protein with a molecular mass of 66 kDa was shown to be selectively repressed when brains were cultured in the presence of 20-HE.     

Organically modified silica nanoparticles are biocompatible and can be targeted to neurons in vivo

The application of nanotechnology in biological research is beginning to have a major impact leading to the development of new types of tools for human health. One focus of nanobiotechnology is the development of nanoparticle-based formulations for use in drug or gene delivery systems. However most of the nano probes currently in use have varying levels of toxicity in cells or whole organisms and therefore are not suitable for in vivo application or long-term use. Here we test the potential of a novel silica based nanoparticle (organically modified silica, ORMOSIL) in living neurons within a whole organism. We show that feeding ORMOSIL nanoparticles to Drosophila has no effect on viability. ORMOSIL nanoparticles penetrate into living brains, neuronal cell bodies and axonal projections. In the neuronal cell body, nanoparticles are present in the cytoplasm, but not in the nucleus. Strikingly, incorporation of ORMOSIL nanoparticles into the brain did not induce aberrant neuronal death or interfered with normal neuronal processes. Our results in Drosophila indicate that these novel silica based nanoparticles are biocompatible and not toxic to whole organisms, and has potential for the development of long-term applications.     

CHOLESTEROL ESTER METABOLIZING ENZYMES IN HUMAN BRAIN: PROPERTIES, SUBCELLULAR DISTRIBUTION AND RELATIVE LEVELS IN VARIOUS DISEASED CONDITIONS

We have in the present study examined the properties and subcellular distribution of cholesterol ester metabolizing enzymes in human brain, and compared the levels of these enzymes in brains from patients with phenylketonuria (PKU), metachromatic leucodystrophy (MLD), and Down's Syndrome (DS). Cholesterol esterification was optimal at pH 5.6, did not require ATP or CoA as cofactors and was inhibited by detergents (TWEEN-20 and Triton X-100) and bile acids (sodium taurocholate and sodium deoxycholate). The specific activity of the cholesterol esterifying enzyme was highest in the mitochondrial fraction. Cholesterol esterifying activity in brains from PKU, MLD, and DS patients was not significantly different. Cholesterol ester hydrolase activity in human brain peaked at two different pHs (4.5 and 6.5). The activity was optimal when the substrate was dispersed in Triton X-100 and sonicated. The specific activity of the pH 4.5 hydrolase was highest in the mitochondrial fraction, while that of the pH 6.5 hydrolase was highest in myelin. The sulfhydryl group reagent parachloromercuribenzoate (PCMB) inhibited the activity of the hydrolase(s) but diisopropylfluorophosphate (DFP), a typical serine reagent, had no effect on hydrolase(s) activity. Addition of either phosphatidyl serine or phosphatidyl inositol significantly enhanced the hydrolase activity at both pHs. The level of cholesterol ester hydrolase(s) in PKU brains was lower than in the brains from DS patients, and the level of these enzymes in the brains from two patients with metachromatic leucodystrophy was lower than in the brains from PKU patients. It is concluded that the properties and subcellular distribution of cholesterol esterifying enzyme in human brain is similar to that in rat brain (Ero & Suzuki , 1971) but that the hydrolases in human brain differ from that in rat brain in several respects, and that the low levels of hydrolase(s) activity in MLD and PKU brain may be related to reduced myelin content of those brains.     

A review of the role of neurosecretion in the control of juvenile hormone synthesis: a tribute to Berta Scharrer

In the 1950s, Berta Scharrer predicted that neurosecretions from the brain regulated corpus allatum activity based upon the observation of the change in localization of neurosecretory material in the brain and change in gland activity after severance of nerves between the brain and corpus allatum. Isolation and characterization of neuropeptide regulators of juvenile hormone production by the corpora allata in the late 1980s has confirmed this prediction. Both a stimulatory allatotropin and an inhibitory allatostatin have been isolated from moth brains. Two families of allatostatins, both quite different from each other and that of moths, have been isolated from cockroaches and crickets.The wide distribution of these peptides in the nervous system, in nerves to visceral muscle, in endocrine cells of the midgut and in blood cells, indicate multifunctions in the insects in which they are allatoregulatory. Some of these other functions have been demonstrated in these insects and in insects in which these neuropeptides occur but do not act as corpus allatum regulators. For the latter group, the neuropeptide regulators of the corpora allata have yet to be isolated. The families of neurosecretory regulators will continue to grow.     

Not all GMOs are crop plants: non-plant GMO applications in agriculture

Since tools of modern biotechnology have become available, the most commonly applied and often discussed genetically modified organisms are genetically modified crop plants, although genetic engineering is also being used successfully in organisms other than plants, including bacteria, fungi, insects, and viruses. Many of these organisms, as with crop plants, are being engineered for applications in agriculture, to control plant insect pests or diseases. This paper reviews the genetically modified non-plant organisms that have been the subject of permit approvals for environmental release by the United States Department of Agriculture/Animal and Plant Health Inspection Service since the US began regulating genetically modified organisms. This is an indication of the breadth and progress of research in the area of non-plant genetically modified organisms. This review includes three examples of promising research on non-plant genetically modified organisms for application in agriculture: (1) insects for insect pest control using improved vector systems; (2) fungal pathogens of insects to control insect pests; and (3) virus for use as transient-expression vectors for disease control in plants.     

Zinc-induced DNA damage and the distribution of metals in the brain of grasshoppers by the comet assay and micro-PIXE

The distribution and concentration of selected elements by PIXE method and DNA damage using comet assay in brains of 1st instars of grasshoppers Chorthippus brunneus from unpolluted (Pilica) and polluted (Olkusz) site, additionally exposed to various doses of zinc during diapause or after hatching, were measured. We tried to assess the degree of possible pre-adaptation of the insects to heavy metals and evaluate the utility of these parameters in estimation of insect exposure to industrial pollutants. Additionally, the mechanism of zinc toxicity for grasshopper brains was discussed. We observed the correlation between experimental zinc dose, zinc contents in the brain and DNA damage in neuroblasts, but only in groups exposed to lower zinc concentration. For higher zinc concentration the amount of the metal in brain and DNA damage remained at the control level. Some site-related differences in DNA damage between grasshoppers from Pilica and Olkusz were observed during short-term exposure (after hatching). Significant increase in the calcium contents in the brain, proportional to zinc concentration in sand, was also observed, especially in the offsprings from Olkusz. The results may be the basis for further searching for molecular mechanisms of defense against heavy metals in insects living in polluted habitats.