Two chemosensory receptors together mediate carbon dioxide detection in Drosophila

Blood-feeding insects, including the malaria mosquito Anopheles gambiae, use highly specialized and sensitive olfactory systems to locate their hosts. This is accomplished by detecting and following plumes of volatile host emissions, which include carbon dioxide (CO2). CO2 is sensed by a population of olfactory sensory neurons in the maxillary palps of mosquitoes and in the antennae of the more genetically tractable fruitfly, Drosophila melanogaster. The molecular identity of the chemosensory CO2 receptor, however, remains unknown. Here we report that CO2-responsive neurons in Drosophila co-express a pair of chemosensory receptors, Gr21a and Gr63a, at both larval and adult life stages. We identify mosquito homologues of Gr21a and Gr63a, GPRGR22 and GPRGR24, and show that these are co-expressed in A. gambiae maxillary palps. We show that Gr21a and Gr63a together are sufficient for olfactory CO2-chemosensation in Drosophila. Ectopic expression of Gr21a and Gr63a together confers CO2 sensitivity on CO2-insensitive olfactory neurons, but neither gustatory receptor alone has this function. Mutant flies lacking Gr63a lose both electrophysiological and behavioural responses to CO2. Knowledge of the molecular identity of the insect olfactory CO2 receptors may spur the development of novel mosquito control strategies designed to take advantage of this unique and critical olfactory pathway. This in turn could bolster the worldwide fight against malaria and other insect-borne diseases.     

Rapid kinetics of second messenger formation in olfactory transduction

Olfactory transduction is thought to be mediated by a membrane-bound receptor protein initiating a multistep reaction cascade which ultimately leads to a depolarizing generator current. There is considerable evidence for the involvement of adenylate cyclase in vertebrate olfactory transduction, and some data indicate that phospholipase C may have a central role in insect olfaction. However, one must show that odorants not only stimulate enzyme activity but also induce changes in concentrations of relevant second messengers. One important criterion for a candidate second messenger of chemo-electrical transduction is that its formation must precede the onset of the odorant-induced membrane permeability changes which proceed on a subsecond time-scale. Here we report an odorant-induced, transient accumulation of cyclic AMP in isolated olfactory cilia from rats, and the generation of inositol trisphosphate in antennal preparations from insects, both of which show subsecond time courses that are sufficiently rapid to mediate the odorant-regulated permeability of olfactory receptor cells.     

Odorant receptors instruct functional circuitry in the mouse olfactory bulb

The mammalian olfactory system detects and discriminates thousands of odorants using many different receptors expressed by sensory neurons in the nasal epithelium. Axonal projections from these neurons to the main olfactory bulbs form reproducible patterns of glomeruli in two widely separated regions of each bulb, creating two mirror-symmetric maps of odorant receptor projections. To investigate whether odorant receptors organize neural circuitry in the olfactory bulb, we have examined a genetically modified mouse line, rI7 --> M71, in which a functionally characterized receptor, rI7, has been substituted into the M71 receptor locus. Here we show that despite their ectopic location the resulting glomeruli are responsive to known ligands of the rI7 receptor, attract postsynaptic innervation by mitral/tufted cell dendrites, and endow these cells with responses that are characteristic of the rI7 receptor. External tufted cells receiving input from rI7 --> M71 glomeruli form precise intrabulbar projections that link medial and lateral rI7 --> M71 glomeruli anatomically, thus providing a substrate for coordinating isofunctional glomeruli. We conclude that odorant receptor identity in epithelial neurons determines not only glomerular convergence and function, but also functional circuitry in the olfactory bulb.     

揭开嗅觉之奥秘

简要介绍了2004年诺贝尔生理学或医学奖得主和获奖成就,并阐述了嗅觉与生活和体育运动的密切关系.     

A gene affecting the specificity of the chemosensory neurons of Drosophila

The sensilla on the proboscis and tarsi of Drosophila contain five neurons, four chemosensory and one mechanosensory. The sugar-sensitive neuron, designated S, carries independent acceptor sites for pyranose, furanose and trehalose. Two others, L1 and L2, respond to salts. The fourth neuron, W, is inhibited by salts and sugars, and is believed to mediate detection of water. We describe here a gene in which mutations alter the neurons in such a way that the S cell is excited by salts. As a result, the mutant flies are strongly attracted by NaCl at concentrations which are repellent to the wild type. To our knowledge, this is the first instance of a mutation which changes the specificity of the chemosensory neurons.     

A single class of olfactory neurons mediates behavioural responses to a Drosophila sex pheromone

Insects, like many other animals, use sex pheromones to coordinate their reproductive behaviours. Volatile pheromones are detected by odorant receptors expressed in olfactory receptor neurons (ORNs). Whereas fruit odours typically activate multiple ORN classes, pheromones are thought to act through single dedicated classes of ORN. This model predicts that activation of such an ORN class should be sufficient to trigger the appropriate behavioural response. Here we show that the Drosophila melanogaster male-specific pheromone 11-cis-vaccenyl acetate (cVA) acts through the receptor Or67d to regulate both male and female mating behaviour. Mutant males that lack Or67d inappropriately court other males, whereas mutant females are less receptive to courting males. These data suggest that cVA has opposite effects in the two sexes: inhibiting mating behaviour in males but promoting mating behaviour in females. Replacing Or67d with moth pheromone receptors renders these ORNs sensitive to the corresponding moth pheromones. In such flies, moth pheromones elicit behavioural responses that mimic the normal response to cVA. Thus, activation of a single ORN class is both necessary and sufficient to mediate behavioural responses to the Drosophila sex pheromone cVA.     

二级破碎石料沥青混合料性能的研究

通过沥青与矿料的粘附性、水稳性及混合料结构的分析来研究一级破碎料组成的混合料和二级破碎料组成的混合料的性能对比。     

A novel class (H3) of histamine receptors on perivascular nerve terminals

Two types of histamine receptor, the H1- and H2-receptors, are found not only on vascular smooth muscle cells but on the perivascular autonomic nerve terminals. Activation of the prejunctional histamine receptors modifies transmitter release from the nerve terminals. Recently, histamine was shown to inhibit its own release from depolarized slices of rat cerebral cortex. This phenomenon was found to be mediated by a novel class of histamine receptor, the H3-receptor, that was pharmacologically distinct from the H1- and H2-receptors. Up to now, there has been no indication whether this third class of histamine receptor is present in any tissue other than the brain. We report here that histamine depresses sympathetic neurotransmission in the guinea-pig mesenteric artery by interacting with histamine H3-receptors on the perivascular nerve terminals. The pharmacological properties of these receptors are similar to those reported for the H3-receptors in the brain. Our data provide evidence for the existence of H3-receptors in the autonomic nervous system.     

一类二次系统存在极限环的充分条件

在平面二次系统(Ⅱ)类方程形式为{dx/dt=-y δx lx^2 mxy ny^2 dy/dt=x(1 ax),(a≠0),的基础上做了一些研究．给出了当n=0,m=-a,l-aδ≠0时,二次系统(Ⅱ)类方程形式为{dx/dt=-y δx lx^2-axy dy/dt=x(1 ax),(a≠0)。存在极限环的一个充分条件。     

Identification of a new class of steroid hormone receptors

The gonads and adrenal glands produce steroids classified into five major groups which include the oestrogens, progestins, androgens, glucocorticoids and mineralocorticoids. Gonadal steroids control the differentiation and growth of the reproductive system, induce and maintain sexual characteristics and modulate reproductive behaviour. Adrenal steroids also influence differentiation as well as being metabolic regulators. The effects of each steroid depend primarily on its specific receptors, the nature of which could therefore provide a basis for classification of steroid hormone action. The successful cloning, sequencing and expression of the human glucocorticoid (hGR) (ref. 1), oestrogen (hER), progesterone (hPR), and mineralocorticoid (hMR) receptors, complementary DNA, plus homologues from various species, provides the first opportunity to study receptor structure and its influence on gene expression. Sequence comparison and mutational analysis show structural features common to all groups of steroid hormone receptors. The receptors share a highly conserved cysteine-rich region which functions as the DNA-binding domain. This common segment allows the genome to be scanned for related gene products: hMR cDNA for example, was isolated using an hGR hybridization probe. In this study, using the DNA-binding domain of the human oestrogen receptor cDNA as a hybridization probe, we have isolated two cDNA clones encoding polypeptides with structural features suggestive of cryptic steroid hormone receptors which could participate in a new hormone response system.     

一类二阶常微分方程解的渐近性态

给出了方程x..+A(t)x.+B(t) =0所有解有界的一个充分条件与零解全局渐近稳定的一个充分条件 ,并进一步给出了方程x..+A(t)x.+B(t)x =e(t)存在唯一稳定周期解的一个充分条件。     

关于一类二阶线性微分方程解的增长性

考虑二阶复线性微分方程f″+Af'+Bf=0解的增长性,其中A(z)是满足杨张极值p=q2的有穷级整函数,赋予系数B(z)适当条件,保证方程的每一个非零解是无穷级的。     

一类二阶拟线性差分方程的非振动性定理

研究了二阶拟线性差分方程Δ（Pnφ（Δxn)) f(n,xn)=0的渐进性，并给出了当任给k≠0，∑∞n=n0|φ^-1(k/pn)|=∞时此方程存在A∞^c,Ac^0型非振动解的充要条件以及存在A∞^0型非振动解的充分条件。     

A second human interleukin-2 binding protein that may be a component of high-affinity interleukin-2 receptors

Although activated human T and B lymphocytes express both high-affinity and low-affinity membrane receptors for interleukin-2 (IL-2), the structural features that distinguish these receptors have remained unresolved. The high-affinity receptors appear to mediate IL-2 induced T cell growth and internalization of IL-2, whereas no function has yet been ascribed to the low-affinity receptors. The Tac antigen is an IL-2 binding protein of relative molecular mass 55,000 (Mr 55K) that participates in the formation of both high- and low-affinity receptors. But Tac complementary DNA transfection and membrane fusion studies have suggested that additional T-cell components are required to produce high-affinity IL-2 receptors. In this study, we report the identification of a second human IL-2 binding protein that (1) has an Mr of approximately 70K, (2) lacks reactivity with the anti-Tac antibody, (3) binds IL-2 with intermediate affinity and (4) is present on the surface of resting T cells, large granular lymphocytes (natural killer cells), and certain T and B cell lines in the absence of the Tac antigen. Chemical crosslinking of 125I-labelled IL-2 bound to high-affinity IL-2 receptors produces labelling of both the p70 protein and the Tac antigen and the anti-Tac antibody blocks the crosslink detection of both of these proteins. Expression of Tac cDNA in a T cell line expressing the p70 protein, but lacking both Tac and high-affinity receptors, results in the reconstitution of high-affinity IL-2 receptors in these cells. Together, these findings suggest that the high-affinity human IL-2 receptor may be a membrane complex composed of at least the p70 protein and Tac antigen.     

一类二阶奇异非线性特征值问题的正解

允许非线性项f在[0,1]x[0,+∞]的边界上奇异,得到了二阶非线性特征值问题     

关于一类二阶非线性差分方程的无界解

研究一类二阶非线性差分方程的无界解.给出此方程的任意无界解序列存在偶(奇)子列趋于∞,奇(偶)子列趋于某一非负数.同时也证明这两种情形下初始条件所在的两平面集被正平衡点的全局稳定流形所分开.     

一类非线性矩阵二阶系统的反馈LPV化控制

针对一类非线性矩阵二阶系统提出了反馈LPV（linear parameter—varying）控制方法．当满足一定条件时,通过引入给定形式的非线性状态反馈将该类非线性系统化为polytopic LPV系统,进而可以采用LPV控制方法进行控制律设计．以hub—beam系统的SFOAC模型为例,通过非线性状态反馈将该模型转化为polytopic LPV系统,然后针对该系统设计线性状态反馈控制律实现区域极点配置,并把该控制律参数的求解转化为LMI约束下的凸优化问题．最后,数值算例验证了该方法的有效性．     

一类二阶线性椭圆型方程的爆破解

应用摄动方法、极大值原理及二阶线性常微分方程理论讨论了Poisson方程△u=k（x）在球域和整个空间上爆破解的存在性。