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.     

单细胞基因组学分析的技术前沿

基因组学已经深刻地改变了生命科学的诸多领域的面貌。目前它的主要内容是新的全基因组碱基序列的测定和在全基因组范围内鉴定那些在不同水平上影响生命活动的基因群的功能和相互作用。为达此要求,近年出现的第二代测序(深度测序)技术和基因芯片技术发挥了关键作用,但是两者都需要足够的高质量的核酸样品。所以,在只有或只能用单细胞或极少量细胞的情况下,如果没有特殊手段,上述分析往往不能常规、方便地进行。文章以DNA扩增为主线,综合阐述了目前在单细胞(特别是微生物)全基因组测序和大基因组的靶向重测序,以及对单细胞或微量细胞进行的基于深度测序或芯片杂交的功能基因组分析,如转录组、ChIP和DNA的CpG甲基化分析等的最新策略和技术,评价了单细胞基因组测序和功能基因组学各技术的特点并对发展前景进行了展望。     

Stem cells in neurogenetics

Genetically controlled proliferation and differentiation of stem nerve cells have been demonstrated to be among the repair mechanisms of the nervous system. Another such process is differentiation of neuroblasts from the cambial reserve.     

Technological advances and genomics in metazoan parasites

Molecular biology has provided the means to identify parasite proteins, to define their function, patterns of expression and the means to produce them in quantity for subsequent functional analyses. Whole genome and expressed sequence tag programmes, and the parallel development of powerful bioinformatics tools, allow the execution of genome-wide between stage or species comparisons and meaningful gene-expression profiling. The latter can be undertaken with several new technologies such as DNA microarray and serial analysis of gene expression. Proteome analysis has come to the fore in recent years providing a crucial link between the gene and its protein product. RNA interference and ballistic gene transfer are exciting developments which can provide the means to precisely define the function of individual genes and, of importance in devising novel parasite control strategies, the effect that gene knockdown will have on parasite survival.     

Technological advances in the molecular biology of Leptospira

Pathogenic members of the genus Leptospira have been refractory to genetic study due to lack of known mechanisms of genetic exchange. To bypass this limitation, several techniques have been useful for Leptospira gene discovery, including heterologous complementation of Escherichia coli mutants, screening of DNA libraries with probes, and random sequence analysis. Construction of combined physical and genetic maps revealed the presence of two circular chromosomal replicons. The organization of the L. interrogans genome is quite variable, with genetically similar strains differentiated by many rearrangements. These rearrangements likely occur through recombination between repetitive DNA elements found scattered throughout the genome. Analysis of intervening sequences and genes encoding LPS biosynthetic enzymes provide evidence of lateral transfer of DNA between Leptospira spp. We have also gained insight into the biology of these bacteria by analyzing genes encoding LPS and outer membrane proteins (OMPs). Some of these OMPs are differentially expressed. Characterization of mechanisms governing the expression of the OMP genes should provide insight into host-parasite interactions. Furthermore, recent advances in heterologous expression of leptospiral OMP genes are opening new avenues of vaccine development.     

Technological advances in minimally invasive radiofrequency ablation of cardiac tissues

Ablative techniques have been sought in many circumstances as alternatives to surgical resection/incision. Besides being minimally invasive, potential benefits of ablation include greater speed and improved access to target tissue compared with other surgical techniques. There is a wide variety of ablation technologies currently in use for medical treatment. These include but are not limited to tissue heating by radiofrequency (RF) current, microwaves, laser, and high intensity ultrasound. RF is among the most heavily used because of its relatively low complexity and cost. Ablative techniques have proven to be viable alternatives to surgical resection/incision of tissue. Although there are other means of tissue heating besides RF, RF is the most commonly used technique in operating rooms because of the reliability of transmural lesions and the low complexity of the system. Optimal systems account for the heterogeneous nature of tissue and variations in tissue property through the ablation cycle. It is important to monitor and assure adequate energy delivery by selecting the appropriate configuration of devices. Energy delivery varies between the various generators and systems, some more responsive than others with relative to changes in tissue impedance that will affect the end results of the operation.     

Bacterial olfaction

Sensing their environment is a crucial ability of all life forms. In higher eukaryotes the sensing of airborne volatile compounds, or olfaction, is well developed. In plants, slime moulds and yeast there is also compelling evidence that these organisms can smell their environment and respond accordingly. Here we show that bacteria are also capable of olfaction. Bacillus licheniformis was able to sense airborne volatile metabolites produced by neighbouring bacterial cultures and cells could respond to this chemical information in a coordinated way. When Bacillus licheniformis was grown in a microtitre plate adjacent to a bacterial culture of the same or a different species, growing in complex medium, biofilm formation and pigment production were elicited by volatile molecules. A weaker response occurred in increasingly distant wells. The emitted volatile molecule was identified as ammonia. These data demonstrate that B. licheniformis has evolved the ability collect information about its environment from the surrounding air and physiologically respond to it in a manner similar to olfaction. This is the first time that a behavioural response triggered by odorant molecules received through the gas phase is described in bacteria.     

Decoding olfaction in Drosophila

Recent experiments in Drosophila demonstrate striking stereotypy in the neural architecture of the olfactory system. Functional imaging experiments in mammals and honeybees suggest a mechanism of odor coding that translates discrete patterns of activity in olfactory glomeruli into an odor image. Future experiments in Drosophila may permit a direct test of this odor-coding hypothesis.     

Speed-accuracy tradeoff in olfaction

The basic psychophysical principle of speed-accuracy tradeoff (SAT) has been used to understand key aspects of neuronal information processing in vision and audition, but the principle of SAT is still debated in olfaction. In this study we present the direct observation of SAT in olfaction. We developed a behavioral paradigm for mice in which both the duration of odorant sampling and the difficulty of the odor discrimination task were controlled by the experimenter. We observed that the accuracy of odor discrimination increases with the duration of imposed odorant sampling, and that the rate of this increase is slower for harder tasks. We also present a unifying picture of two previous, seemingly disparate experiments on timing of odorant sampling in odor discrimination tasks. The presence of SAT in olfaction provides strong evidence for temporal integration in olfaction and puts a constraint on models of olfactory processing.     

Perireceptor events in olfaction

Before reaching olfactory receptor neurons, odorant molecules have to cross an aqueous interface: the nasal mucus in vertebrates and the sensillar lymph in insects. Biochemical interactions taking place between odorants and the elements of these phases are called perireceptor events. Main protein constituents of these media, in both insects and vertebrates, are OBPs (odorant-binding proteins). Another class of proteins active in the olfactory perireceptor area includes odorant-degrading enzymes. The structure and the properties of these major proteins, with particular reference to OBPs, are reviewed and their role in olfactory transduction is discussed. © 1996 John Wiley & Sons, Inc.     

The cell biology of malaria infection of mosquito: advances and opportunities

Recent reviews (Feachem et al.; Alonso et al.) have concluded that in order to have a sustainable impact on the global burden of malaria, it is essential that we knowingly reduce the global incidence of infected persons. To achieve this we must reduce the basic reproductive rate of the parasites to < 1 in diverse epidemiological settings. This can be achieved by impacting combinations of the following parameters: the number of mosquitoes relative to the number of persons, the mosquito/human biting rate, the proportion of mosquitoes carrying infectious sporozoites, the daily survival rate of the infectious mosquito and the ability of malaria‐infected persons to infect mosquito vectors. This paper focuses on our understanding of parasite biology underpinning the last of these terms: infection of the mosquito. The article attempts to highlight central issues that require further study to assist in the discovery of useful transmission‐blocking measures.     

Molecular neurogenetics of sexual differentiation and behaviour

Sex and death. Two things that come once in a lifetime. Only after death you're not nauseous. - Woody Allen 'Sleeper'. The brain and nervous system functions that underlie sex-specific behaviour are of obvious importance to all animals, including humans. To understand behaviour related to sex, it is important to distinguish those aspects that are controlled genetically. Much of the recent progress in studies of the molecular neurogenetics of sexual differentiation and behaviour has come from the use of genetically tractable organisms (i.e. fruitflies and nematode worms) that exhibit a full range of sexually dimorphic phenotypes.     

Behavioral genetics and neurogenetics and their development in Russia

The problems of behavioral genetics and neurogenetics and development of these fields in Russia are considered.     

Odors and olfaction

In this review, we discuss some of the neural processes involved in the perception of odors that, together with audition and vision, provide essential information for analyzing our surroundings. We shall see how odor detection and learning induce substantial structural and functional changes at the first relay of the olfactory system, i.e., the main olfactory bulb. Among the mechanisms that participate in these modifications is the persistence of a high level of interneuron neurogenesis within the adult olfactory bulb. Our goal is to present some observations related to the neurogenesis that may aid in understanding the neural mechanisms of sensory perception and shed light on the cellular basis of olfactory learning. We summarize the current ideas concerning the molecular mechanisms and organizational strategies used by the olfactory system to transduce, encode, and process information at various levels in the olfactory sensory pathway. Due to space constraints, this review focuses exclusively on the olfactory systems of vertebrates and primarily those of mammals.