A preliminary study for identifying olfactory markers of fear in the rat

In stressful situations, many animals release alarm pheromones to warn conspecifics of impending danger. The authors sought to establish experimental conditions for a larger study aimed at identifying alarm pheromones emitted by the rat. They placed rats in a specially designed chamber and exposed them to aversive tactile, visual and acoustic stimuli over the course of a few days. The researchers observed rats' behavior and analyzed air samples taken from their immediate environment under the following conditions: (i) when rats were unstressed; (ii) immediately after rats were exposed to aversive stimuli; and (iii) when rats were left alone in the chamber after being conditioned to fear imminent aversive stimuli. Stressed rats emitted several substances that are known to function as alarm pheromones in insects. When previously unstressed control rats were exposed to these same substances, they had a distinct behavioral fear response.     

Enfleurage, lipid recycling and the origin of perfume collection in orchid bees

Enfleurage, the extraction of elusive floral scents with the help of a lipophilic carrier (grease), is widely used in the perfume industry. Male neotropical orchid bees (Euglossini), which accumulate exogenous fragrances as pheromone analogues, use a similar technique. To collect fragrances, the bees apply large amounts of straight-chain lipids to odoriferous surfaces from their cephalic labial glands, which dissolve the volatiles, and the mixture is then transferred to voluminous hind-leg pockets. Here, we show that males do in fact operate a lipid conveyor belt to accumulate and concentrate their perfume. From the hind-leg pockets of caged male Euglossa viridissima, deuterated derivatives of carrier lipids were consecutively sequestered, shuttled back to the labial glands and reused on consecutive bouts of fragrance collection. Such lipid cycling is instrumental in creating complex perfume bouquets. Furthermore, we found that labial glands of male orchid bees are strikingly similar to those of scent-marking male bumblebees in terms of size, form and structure. This, and a prominent overlap in secretory products, led us to propose that perfume collection evolved from scent-marking in ancestral corbiculate bees.     

Practical applications of research into the regulation of plant volatile emission

Throughout their life cycles, plants release diverse blends of volatile compounds that play crucial roles in pollinator attraction, defense and communication. The importance of plant volatiles, in addition to the general appeal of fragrances and flavors to humans, have made these secondary metabolites a target for metabolic engineering. In the past decade, significant discoveries in the plant volatile biosynthetic pathways have provided a starting point for their modification. Pioneering attempts to alter plant volatile profiles have uncovered the complexity of networks and their regulation, and have built new avenues for future successful metabolic engineering.     

Semi-volatile organic compounds at the leaf/atmosphere interface: numerical simulation of dispersal and foliar uptake

The behaviour of (semi-)volatile organic compounds at the interface between the leaf surface and the atmosphere was investigated by finite-element numerical simulation. Three model systems with increasing complexity and closeness to the real situation were studied. The three-dimensional model systems were translated into appropriate grid structures and diffusive and convective transport in the leaf/atmosphere interface was simulated. Fenpropimorph (cis-4-[3-(4-tert-butylphenyl)-2-methylpropyl]-2,6-dimethylmorpholine) and Kresoxim-methyl ((E)-methyl-2-methoxyimino-2-[2-(o-tolyloxy-methyl)phenyl] acetate) were used as model compounds. The simulation showed that under still and convective conditions the vapours emitted by a point source rapidly form stationary envelopes around the leaves. Vapour concentrations within these unstirred layers depend on the vapour pressure of the compound in question and on its affinity to the lipoid surface layers of the leaf (cuticular waxes, cutin). The rules deduced from the numerical simulation of organic vapour behaviour in the leaf/atmosphere interface are expected to help in assessing how (semi-)volatile plant products (e.g. hormones, pheromones, secondary metabolites) and xenobiotics (e.g. pesticides, pollutants) perform on plant surfaces.     

Pheromonal communication involved in courtship behavior in Diptera

Sex pheromones are known for many dipteran species and play an important role in courtship behavior, together with visual, tactile, acoustic and other factors. Pheromones for a number of dipterans have been recently identified. This survey covers a number of species in all the families that have been studied. The review discusses diverse courtship behaviors in Diptera, with a special focus on the sex pheromones involved. In the Nematocera suborder, pheromones are volatile components, which act at a distance. They are derived from short-chain alkanes with acetoxy groups (Cecidomyidae) or terpenes (Psychodidae). In the Cyclorrhapha, pheromones may be volatile, derived from alkanes (Tephritidae) or terpenes (Agromyzidae), or non-volatile, unsaturated or methyl-branched hydrocarbons, which act by contact (the other subgenera). The behavioral roles and regulation of these pheromones are described, and their importance in species recognition is discussed.     

LIGHT INTENSITY AND THE TIMING OF DAILY ACTIVITY OF FINCHES (FRINGILLIDAE)

The prevailing general theory of entrainment of endogenous circadian rhythms explains variation in the timing of activity with season, latitude and weather conditions on the basis of the dependence of spontaneous frequency of the rhythm on the intensity of constant illumination. In an experiment designed to test the validity of this theory, Greenfinches and chaffinches were exposed to the natural light-dark cycle alternately in full illumination and in reduced daylight. Contrary to prediction by current hypotheses for these species, in which the spontaneous frequency decreases with decreasing light intensity, their midpoint of daily activity shifted forward when the intensity of natural daylight was reduced. This result refutes the hypothesis that light affects the timing of activity in nature in a manner predictable from its effect in constant conditions.
Both species of finches have a bimodal daily distribution of perch-hopping activity. The morning peak and evening peak of activity are of about equal strength in winter, but the morning peak increases sharply in the reproductive season. The possibility that the two peaks represent two pacemaker systems, under differential endocrine control, is discussed.
The precision in the timing of daily onset and end of activity is positively correlated with the estimated average rate of change of light intensity at these times of day. Thus, day-to-day variations are markedly increased in reduced daylight when activity begins late after sunrise and terminates well before sunset.     

Production and evolution pattern of “fruity smell” aggregation pheromones in genus Drosophila

Insects produce pheromones to serve a range of ecological functions throughout their lifetime. The chemical composition, production pattern, and interspecies specificity provide information for carrying out their function and biological significance. Several species of Drosophila produce a class of volatile esters considered as “fruity smells”; however, the production pattern and ecological functions of these “fruity smell” volatiles in genus Drosophila are poorly understood. Here, using the headspace solid-phase microextraction (SPME) method, we tested the production pattern of volatile pheromones in Drosophila immigrans and factors that possibly affected pheromone production, including mating, feeding conditions, age of adult flies, and geographical distribution. We also explored the evolution and production pattern of volatile pheromones in 14 species of genus Drosophila. Our result showed that male D. immigrans adult flies produce three male-specific volatile ester pheromones, which are also considered as “fruity smell” chemicals, in a relatively stable pattern. In addition, a series of “fruity smell” ester pheromones with similar structure and chemical properties were found to appear in the species of D. virilis and D. immigrans species group, but not in the species of D. melanogaster species group. The ester volatile pheromone production of male flies has a correspondence with the female's demand for host plants. Integrating the production and evolution pattern of these volatile chemicals, we inferred the interaction between insects and host plants reflected in the Drosophila “fruity smell” pheromones.     

Reactions of five species of stingless bees to some volatile chemicals and to other species of bees

Trigona pectoralis and T. mexicana attacked when volatile chemicals that have been identified from their heads were presented at the nest entrance; mixtures approximating the composition of the head extracts elicited stronger reactions than did any of the single chemicals. Alarm pheromones of T. pectoralis occur in approximately equal concentrations in the mandibular glands and the remainder of the heads; other alarm pheromones occur in small concentrations in the abdomen. Three other species of stingless bees gave defensive reactions when presented with the mixture of chemicals, with some of the single chemicals, with living or freshly killed T. pectoralis, or with the heads of that species. Living or freshly killed Lestrimelitta limao, which are known to live by robbing other bees, elicited strong defence reactions from all species; citral, the major volatile component of the head extract of L. limao, gave similar results. Variations in the strength of reactions of bees to other species and to a wide variety of volatile chemicals led to the conclusion that bees probably learn to recognize the odour of other species that rob from their nests, and that the pheromones of the robbing species are allomones that recruit the victims to the defence of the nest. It is postulated that the reactions to some of the chemicals developed because the bees had been exposed to enemies that contained the chemicals. It is often impossible to decide whether the reactions of bees to a chemical result from an inability to distinguish the chemical from some other, or from the properties and usual origin of the chemical itself.Some of the problems that arise from the reactions of the bees, and particularly from their reactions to 2-heptanone, geraniol, and benzoic acid, are discussed.     

Aphid Acceptance of Barley Exposed to Volatile Phytochemicals Differs Between Plants Exposed in Daylight and Darkness

It is well known that volatile cues from damaged plants may induce resistance in neighboring plants. Much less is known about the effects of volatile interaction between undamaged plants. In this study, barley plants, Hordeum vulgare cv. Kara, were exposed to volatiles from undamaged plants of barley cv. Alva or thistle Cirsium vulgare, and to the volatile phytochemicals, methyl salicylate or methyl jasmonate. Exposures were made either during natural daylight or darkness. Acceptance of exposed plants by the aphid Rhopalosiphum padi was assessed, as well as the expression of putative marker genes for the different treatments. Aphid acceptance of plants exposed to either barley or C. vulgare was significantly reduced, and an effect of the volatiles from undamaged plants was confirmed by the induction of pathogenesis-related protein, PR1a in exposed plants. However the effect on aphid acceptance was seen only when plants were exposed during darkness, whereas PR1a was induced only after treatment during daylight. Aphid acceptance of plants exposed to either methyl salicylate or methyl jasmonate was significantly reduced, but only when plants were exposed to the chemicals during daylight. AOS2 (allene oxide synthase) was induced by methyl jasmonate and BCI-4 (barley chemical inducible gene-4) by methyl salicylate in both daylight and darkness. It is concluded that (a) the effects on aphids of exposing barley to volatile phytochemicals was influenced by the presence or absence of light and (b) the response of barley to methyl salicylate/methyl jasmonate and to volatiles from undamaged plants differed at the gene and herbivore level.Key Words: methyl jasmonate, methyl salicylate, allelobiosis, barley, PR1, allene oxide synthase, Rhopalosiphum padi, light     

天牛性信息素、引诱植物和植物性引诱剂的研究与应用

由于目前所拥有的各种天牛防治方法都难以获得理想的防治效果,研发新型天牛控制技术势在必行。其中利用引诱剂是最具潜力的研究领域之一。对天牛的性信息素、引诱植物和植物性引诱剂3个方面的研究及应用作了综述。天牛雌、雄成虫均可释放性信息素进行两性间的通讯联系。天牛性信息素的分泌部位因天牛种类不同而存在着差异。雄、雌成虫触角上均有感受性信息素的感受器,但报道较多的是雄虫感受器。迄今已鉴定出13种天牛性信息素的化学结构。一般而言,天牛成虫的嗜食树种,对天牛具有较强的引诱作用,可作为诱饵树种使用。寄主植物的某些挥发性物质对天牛成虫也有独特的引诱效果。除此之外,对天牛性信息素、引诱植物和植物性引诱剂研究与应用中存在的困难也进行了讨论,并对它们的应用前景做了展望。     

Release of male courtship display in Periplaneta americana: evidence for female contact sex pheromone

Male American cockroaches (Periplaneta americana) are attracted to virgin females by volatile sex pheromones. After antennal contact with the female they turn through 180° and spread their wings in courtship display. A chemical contact stimulus releasing male courtship is demonstrated in the female cuticle. Experiments with standardized olfactory stimulation by volatile sex pheromones revealed that the contact stimulus is sex-specific and species-specific. It can be washed off the cuticle with non-polar solvents and was successfully transferred to glass dummies. However, it is not effective in the absence of volatile sex pheromones. Thus volatile sex pheromones are responsible for male attraction and sexual motivation, while mate recognition is accomplished through the contact pheromone.     

Behavioural responses of female Neogobius melanostomus to odours of conspecifics

The behavioural responses of reproductive and non‐reproductive female round gobies Neogobius melanostomus to water conditioned by reproductive and non‐reproductive males and females were tested. The behavioural responses of reproductive female round gobies exposed to odour of reproductive males included increased time spent near the source of the odour, elevated swimming velocities and directed movement to and around the odour source when compared with their responses to control water. These results suggested that pheromones released from reproductive males may induce spawning behaviour in reproductive females. Non‐reproductive females exposed to reproductive female odour spent significantly more time near the odour source of reproductive females compared with control water. Non‐reproductive females also showed directed movement towards and around the odour source when exposed to reproductive female odour. These results suggested that round gobies use inter‐sexual and intra‐sexual pheromones and that both sex and reproductive status are important in the detection and release of these pheromones.     

cDNA cloning and in situ hybridization of Delta11-desaturase, a key enzyme of pheromone biosynthesis in Ostrinia scapulalis (Lepidoptera: Crambidae)

Female sex pheromones are considered to be produced in a "pheromone gland" located in the terminal abdominal segments (8th-10th, TAS) of a moth; however, in many moth species, the cells that produce pheromones have not actually been specified. We investigated cells in the TAS that synthesize pheromones in the adzuki bean borer Ostrinia scapulalis, by locating pheromones and their precursors, and mRNA for Delta11-desaturase, a key enzyme in pheromone biosynthesis. We demonstrated that the pheromone components, (E)-11- and (Z)-11-tetradecenyl acetates, and their fatty acyl precursors were specifically contained in the dorsal part of the TAS. A cDNA (OscaZ/E11) that encodes a Delta11-desaturase was cloned from the TAS. RT-PCR and in situ hybridization unequivocally showed that OscaZ/E11 is specifically expressed in the modified epidermal cells located at the dorsal end of the 8th-9th intersegmental membrane.     

Cross-talk between the autocrine (mitogenic) pheromone loop of the ciliate Euplotes raikovi and the intracellular cyclic AMP concentration

Cell type-specific protein signals, called pheromones, are constitutively secreted by Euplotes raikovi and bound back in autocrine fashion, with a positive effect on the vegetative (mitotic) cell growth. In cells growing suspended with their secreted pheromone, it was found that any interruption of this autocrine signaling loop was immediately followed by an effective enhancement of the basal intracellular cyclic AMP (cAMP) level. To establish a cause-effect relationship between these pheromone-induced variations in the cytoplasmic cAMP level and cell growth, cells ready to pass from a resting stage to a new growth cycle were conditioned either to incorporate a cAMP analog resistant to phosphodiesterase degradation, or to utilize cAMP released (following cell irradiation) from incorporated "caged" cAMP. Cells responded at every induced increase in their basal cAMP level by markedly decreasing their commitment to start a new growth cycle. It was deduced that the autocrine signaling of E. raikovi pheromones involves cAMP as inhibitor of its mitogenic activity.     

Influence of host fruit and conspecifics on the release of the sex pheromone By Toxotrypana curvicauda males (Diptera: Tephritidae)

The release of tephritid sex pheromones depends significantly on the age of the male, the social context (presence of conspecifics) and chemical context (host volatiles). In this study, the influence of host fruit and conspecific (males and females) on the emission of the pheromonal compound 2-methyl-6-vinylpyrazine (2,6 mvp) by Toxotrypana curvicauda (Gerstaecker) males was investigated under laboratory conditions. Males were divided into one control group (nonexposed to treatment) and five experimental groups were placed 1 hr before volatile collection with: 1) host fruit (unripe papaya), 2) two females, 3) two males, 4) host fruit plus two females, and 5) host fruit plus two males. The volatiles were sampled by means of solid phase microextraction and analyzed with gas chromatography-mass spectrometry, with a focus on 2,6 mvp. Males emitted volatiles from the first day after adult emergence. The maximum peak and the temporal pattern of 2,6 mvp release were modified by the presence of host fruit and conspecific males or females. On day 5, males in the presence of fruit maintained a constant release of 2,6 mvp while the presence of conspecific caused a decrease of pheromone release. The release of 2,6 mvp was increased significantly in males exposed to both types of stimuli simultaneously. The stimuli (fruit and conspecifics) modified the release of 2,6 mvp, however the effect depended on male age.     

哺乳动物主要嗅觉系统和犁鼻系统信息识别的编码模式

哺乳动物具有两套嗅觉系统, 即主要嗅觉系统和犁鼻系统。前者对环境中的大多数挥发性化学物质进行识别, 后者对同种个体释放的信息素进行识别。本文从嗅觉感受器、嗅球、嗅球以上脑区三个水平综述了这两种嗅觉系统对化学信息识别的编码模式。犁鼻器用较窄的调谐识别信息素成分, 不同于嗅上皮用分类性合并受体的方式识别气味; 副嗅球以接受相同受体输入的肾丝球所在区域为单位整合信息, 而主嗅球通过对肾丝球模块的特异性合并编码信息; 在犁鼻系统, 信息素的信号更多地作用于下丘脑区域, 引起特定的行为和神经内分泌反应。而在主要嗅觉系统, 嗅皮层可能采用时间模式编码神经元群, 对气味的最终感受与脑的不同区域有关。犁鼻系统较主要嗅觉系统的编码简单, 可能与其执行的功能较少有关。     

Thioether Profragrances: Parameters Influencing the Performance of Precursor‐Based Fragrance Delivery in Functional Perfumery

A series of thioether profragrances was prepared by reaction of different sulfanylalkanoates with δ‐damascone and tested for their release efficiencies in a fabric‐softener and an all‐purpose cleaner application. Dynamic headspace analysis on dry cotton and on a ceramic plate revealed that the performance of the different precursors depended on the structure, but also on the particular conditions encountered in different applications. Moreover, profragrances derived from other α,β‐unsaturated fragrance aldehydes and ketones were synthesized analogously and evaluated using the same test protocol. Thioethers were found to be suitable precursors to release the corresponding fragrances, but neither the quantity of profragrance deposited from an aqueous environment onto the target surface, nor the amount of fragrance released after deposition could be linearly correlated to the hydrophilicity or hydrophobicity of the compounds. Different sets of compounds were found to be the best performers for different types of applications. Only one of the compounds evaluated in the present work, namely the thiolactic acid derivative of δ‐damascone, efficiently released the corresponding fragrance in both of the tested applications. Profragrance development for functional perfumery thus remains a partially empirical endeavour. More knowledge (and control) of the various application conditions are required for an efficient profragrance design.     

Petunia flowers solve the defence/apparency dilemma of pollinator attraction by deploying complex floral blends

Flowers recruit floral visitors for pollination services by emitting fragrances. These scent signals can be intercepted by antagonists such as florivores to locate host plants. Hence, as a consequence of interactions with both mutualists and antagonists, floral bouquets likely consist of both attractive and defensive components. While the attractive functions of floral bouquets have been studied, their defensive function has not, and field‐based evidence for the deterrence of floral‐scent constituents is lacking. In field and glasshouse experiments with five lines of transgenic Petunia x hybrida plants specifically silenced in their ability to release particular components of their floral volatile bouquet, we demonstrate that the emission of single floral‐scent compounds can dramatically decrease damage from generalist florivores. While some compounds are used in host location, others prevent florivory. We conclude that the complex blends that comprise floral scents are likely sculpted by the selective pressures of both pollinators and herbivores.     

Synthesis of Photolabile Caged Amino Acids for Measuring Amino Acid Transporters

Photolabile precursors (caged compounds) of amino acids such as Ala, Leu, Lys, and Ser were prepared by some simple reactions. These compounds were designed for the rapid, photochemically initiated release of amino acids. These amino acid transporters were expressed in Xenopus oocyte by injecting mRNA prepared from rat kidney. The electrical response of each transporter was examined by applying the amino acids and caged compounds before and after photolysis. Photolysis of the caged amino acids increased the electrical response of the facilitated amino acid transporters expressed in the oocyte. Consequently, these synthesized caged amino acids would be applicable to kinetic investigations on the transporters when combined with a pulsed laser or xenon arc flash lamp.     

Wickerhamomyces anomalus AS1: a new strain with potential to improve wine aroma

The monoterpenes are the most important contribution to the olfactory profile of wine due to their low odour threshold. These and other aroma-active substances do not generally exist in a free form but are conjugated to mono- or disaccharides, thereby forming water-soluble and odourless complexes. Enzymes that cleave the sugar moieties from the precursors can, therefore, have a major impact on the sensory profile of wine, as they release the volatile aroma compounds. For this reason, we searched for wine yeasts producing glycosidases which are active under oenological conditions. A collection of 100 wine yeasts were screened for glycosidase activities in whole cells and in culture supernatants. Kinetic parameters were determined spectrophotometrically with synthetic model substrates, and hydrolysis of natural glycosides was detected by thin-layer chromatography. A yeast isolate, AS1, was identified as a new Wickerhamomyces anomalus strain which hydrolysed a number of synthetic and natural glycosides under oenological conditions. Citronellol- and nerol-glucosides, among the most frequently occurring aroma precursors in wine, were also cleaved. In contrast to a commercial β-glucosidase, whole cells of W. anomalus AS1 catalysed deglycosylation of arbutin and salicin directly in a white and a red wine. Besides the formation of intra- and extracellular glucoside hydrolases, strain AS1 exhibited arabinosidase and xylosidase activities which are also essential for the release of flavour compounds. Even with limited functionality at oenological conditions, the glycoside hydrolase activities of W. anomalus AS1 may improve aroma development, provided that the reaction occurs over a longer period, as it is the case during wine-making.