Olfactory responses to attractants and repellents in tsetse

The aims of this study were to investigate how antennal olfactory cells of tsetse (Diptera: Glossinidae) code odour quality and how they are able to discriminate between attractive and repellent odours. For Glossina pallidipes Austen, a survey is presented of the cells' responses to attractive (1-octen-3-ol, acetone, 3-methylphenol, carbon dioxide) and repellent stimuli (2-methoxyphenol, acetophenone, lactic acid, naphthalene). In addition, the responses of these cells to binary mixtures and the dose-response curves of 1-octen-3-ol, 3-methylphenol, 2-methoxyphenol and acetophenone are presented. A minority of the cells responded to one attractant or repellent only, whereas the vast majority were excited by more than one of the attractive and/or repellent stimuli. It is proposed that the peripheral olfactory cells of tsetse discriminate between different compounds via an across-fibre pattern coding, in which the cells that specifically code for attractants or repellents may play a substantial role in composing a unique excitation pattern that informs the central nervous system about the specificity of odours.     

酰胺类蚊虫驱避化合物与引诱物氨分子缔合作用的计算

【目的】为了探究驱避机理,此前选择萜类驱避化合物及与DEET(避蚊胺)具有类似结构的酰胺类驱避化合物,开展了驱避化合物与引诱气味组分(L-乳酸、羧酸等)缔合作用对驱避活性影响的研究。为了扩大驱避化合物的类型,本研究选择另外一组43个酰胺类驱避化合物,计算了它们与蚊虫引诱物氨之间的双分子缔合作用,以及该缔合作用对驱避活性的影响,从而为驱避机理研究提供帮助。【方法】用Gaussian 03软件优化驱避化合物单体和双分子缔合体的三维结构式;通过Ampac和Codessa软件建立结构与驱避活性之间的定量构效关系模型。【结果】驱避化合物与氨分子的缔合距离、角度和缔合能量分别是2.2~3.0,128~180°和14~25 k J/mol;最佳四参数模型中R2为0.8987,其中2个参数来自驱避化合物单体,分别是(1/6)X GAMMA polarizability(DIP)和ESPminimum net atomic charge for an H atom,另外2个参数来自双分子缔合体,分别是ESP-DPSA-2 difference in CPSAs(PPSA2-PNSA2)[Quantum-Chemical PC]和Minimum valency of a C atom。模型检验中训练集和测试集的相关系数平方的平均值分别为0.9013和0.8666。【结论】驱避化合物与氨分子之间存在弱氢键力缔合作用,驱避化合物分子的极化度及其与氨分子之间的极性相互作用、缔合体中分子间键相互作用及其电荷分布均对驱避活性产生显著影响,说明双分子缔合对驱避活性具有显著影响。模型检验表明最佳四参数模型具有良好的稳定性和预测能力。本研究可为寻找新型蚊虫驱避剂和揭示蚊虫驱避剂的作用机理提供参考。     

定量计算萜类蚊虫驱避化合物与羧酸缔合作用对其驱避活性的影响

【目的】驱避剂是防止蚊虫叮咬的良好个人防护用品,但其作用机理一直未被解释清楚。本研究利用化学计算手段对4种重要的人体引诱物（乙酸、丙酸、丁酸和戊酸）与22个萜类驱避化合物的缔合作用以及该作用对驱避活性的影响进行了研究,以期为蚊虫驱避机理研究提供新思路。【方法】利用GAUSS View软件构建引诱化合物分子、驱避化合物分子以及二者可能形成的缔合体结构,再利用GAUSSIAN软件优化所有结构,并计算它们的能量和各类参数;借助AMPAC和CODESSA软件计算出所有结构的描述符;以萜类驱避化合物对白纹伊蚊Aedes albopictus校正驱避率的对数值（logCRR）为活性数据,利用CODESSA软件建立描述符与驱避活性的定量构效关系模型。【结果】4种羧酸与萜类驱避化合物相互缔合的缔合能量大多在18~20 kJ/mol之间,缔合距离和角度分别在2.0~2.5 Å 和110°~180°内波动,符合氢键相互作用的特征。4个最优定量构效关系模型的R²值均大于0.9,模型中的参数都包含缔合体的描述符,表明引诱物 驱避物缔合作用与校正驱避率的对数值显著相关。【结论】4种羧酸与萜类驱避化合物之间存在中等强度的氢键缔合作用,该缔合作用对驱避活性具有重要影响。研究初步揭示了引诱物 驱避物缔合作用的存在,也为从新的角度研究蚊虫驱避机理提供了前期研究基础。     

Chemical repellency in birds: relationship between chemical structure and avoidance response.

We examined how molecular structure of 24 anthranilate and benzoic acid derivatives correlated with drinking behavior in European starlings Sturnus vulgaris. The effectiveness of bird repellents was associated with basicity, the presence of an electron-donating group in resonance with an electron-withdrawing carboxylic group on a phenyl ring, and a heterocyclic ring in the same pi cloud plane as the phenyl ring. Of the benzoic acid derivatives tested in this study, methyl, ethyl, dimethyl, and linalyl anthranilate as well as anthranilic acid and 4-ketobenztriazine were repellent to birds. Water consumption was significantly reduced relative to control levels at concentrations as low as 0.05% (weight/volume) for the best repellents. Further statistical tests showed that reduction in consumption for the best repellents was absolute, not significantly different from zero consumption. Anthranilic acid isomers were moderately good repellents. The ability to generate a model predicting repellency allows for the efficient identification and development of ecologically sound, nonlethal, taxa-specific repellents to be used for the protection of wildlife in agricultural and industrial applications.     

Molecular interactions between terpenoid mosquito repellents and human-secreted attractants

Molecular interactions between terpenoid mosquito repellents and three typical human-secreted attractants, ammonia, 1-octen-3-ol, and formic acid were studied. Relative energies, bond distances, and bond angles of the molecular interactions were obtained at HF level to evaluate the interaction intensity and types. The effects of molecular interactions on repellency were investigated by the subsequent quantitative structure–activity relationship (QSAR) study. The results of this study suggest that attractant–repellent interaction should not be ignored and could be helpful for future research on the repelling mechanism of mosquito repellents.     

Trends in arthropod defensive secretions,an aquatic predator assay

Summary Twenty-five arthropod defensive chemicals were tested on a potential fish predator to assay basic repellency, interniche effectiveness and mimetic interactions among repellents, and predator tolerance to repellents.The defensive secretions of aquatic arthropods are more effective repellents than those of terrestrial or cryptozoic arthropods. Phenolic compounds are more effective than carbonylic or acidic compounds. Repellency is most effective in compounds of reduced water solubility. Repeated exposure to gradually increasing molar concentrations of benzoic acid resulted in a greater acceptability of this compound to fish predators. It is suggested that Mullerian mimicry systems based on large numbers of species may be susceptible to dilution effects in terms of effectiveness.     

Regulation of lactate production and utilization in rat tumors in vivo

These experiments were performed to determine the factor(s) that regulate lactic acid production and utilization by rat tumors in vivo. Arteriovenous differences for glucose and lactic, pyruvic, 3-OH-butyric, and acetoacetic acids were measured across "tissue-isolated" Walker 256 sarcocarcinomas and Morris 5123C hepatomas in fasted rats anesthetized with sodium pentobarbital. Twenty-six per cent of the sarcocarcinomas (n = 53) and 48% of the hepatomas (n = 29) utilized blood lactic acid. The remainder released lactic acid into the venous blood. The steady-state rate of glucose consumption was similar in both lactate-producing and lactate-utilizing tumors. The range of lactate concentrations in the blood leaving the tumors was narrower than the range of lactate concentrations in the blood entering the tumors. This difference was caused by tumor lactic acid production at low arterial lactate concentrations and tumor lactic acid utilization at high arterial lactate concentrations. Individual tumors changed from lactic acid production to lactic acid utilization in a matter of minutes in response to an increase in the arterial lactic acid concentration. Mean lactic plus pyruvic acid concentrations and lactic/pyruvic acid ratios in the tumor venous blood were 2.15 +/- 0.22 and 23.4 +/- 3.7 mM, respectively, for Walker sarcocarcinoma 256 (n = 18) and 1.28 +/- 0.13 and 48.1 +/- 5.1 mM, respectively, for hepatoma 5123C (n = 11). The results suggest: that a steady-state lactic plus pyruvic acid concentration and lactic/pyruvic acid ratio are maintained in the tumor cell cytoplasm by the active glycolytic pathway and by lactic acid dehydrogenase; that the tumor intracellular concentrations equilibrate with the arterial blood and that the tumor steady state is expressed in the tumor venous blood; and that tumor lactic acid production or utilization results from the equilibration between the variable arterial lactic acid concentration and the more constant tumor intracellular steady-state lactic acid concentration. Since the arterial lactate concentration may be less than, greater than, or equal to the intracellular steady-state concentration, an individual tumor may produce, utilize or neither produce nor utilize lactic acid.     

Negative chemotaxis inSpirochaeta aurantia

A repellent-gradient tube assay for negative chemotaxis inSpirochaeta aurantia was developed and used to demonstrate that acids, alcohols, and sulfide were effective chemorepellents. The threshold concentrations (the lowest concentration of a repellent that elicited a detectable response) for benzoic acid, salicylic acid, and butyric acid were 3×10^–5 M. For acetic acid, propionic acid,p-aminobenzoic acid, propanol, butanol, and sulfide, threshold concentrations were 10^–3 to 10^–4 M. For formic acid, glyoxylic acid, glycolic acid, lactic acid, malonic acid, succinic acid, fumaric acid, methanol, ethanol, ethanediol, and propanediol, threshold concentrations were 10^–2 to 10^–3 M. Compounds such as methylamine, ethanolamine, formaldehyde, benzene, toluene, phenol, indol, nickel, and various amino acids did not elicit a repellent response. The results of competition experiments suggest that the repellents identified are recognized by three distinct receptors: a weak acid receptor, an alcohol receptor, and a sulfide receptor. The repellent responses to weak acids were maximal at pH 5.5 and decreased with increasing pH, whereas the response to propanol was unaffected by pH over a range of 5.5–8.0. The demonstration of negative chemotaxis inS. aurantia and the identification of distinct classes of repellents will allow further experimentation directed at understanding chemosensory mechanisms in spirochetes.     

Isolation and identification of lactic acid bacteria from soil using an enrichment procedure

AIMS: To survey, and identify and classify the ecological distribution of lactic acid bacteria from soil in Japan and Taiwan. METHODS AND RESULTS: Acid-producing bacteria were isolated from 68 soil samples, collected from Japan and Taiwan, in the rhizospheres of fruit trees, from the floor of a henhouse and around a horse farm. All isolates were identified by physiological and genetic tests. Thirty-two of the 54 isolates were identified as lactic acid bacteria (LAB), 16 as spore-forming lactic acid bacteria, five as Clostridium and one as Bacillus. These lactic acid bacteria represent five genera: Lactobacillus, Lactococcus, Enterococcus, Leuconostoc and Weissella. CONCLUSIONS: A high rate of isolating lactic acid bacteria was obtained from soil. SIGNIFICANCE AND IMPACT OF THE STUDY: This study suggests that soil may be a common source for the isolation of lactic acid bacteria.     

Impact of lactic acid on cell proliferation and free radical‐induced cell death in monolayer cultures of neural precursor cells

Biomaterials prepared from polyesters of lactic acid and glycolic acid, or a mixture of the two, degrade in the presence of water into the naturally occurring metabolites, lactic acid and glycolic acid. While the lactic acid degradation product that is released from biomaterials is well tolerated by the body, lactic acid can influence the metabolic function of cells; it can serve as an energy substrate for cells, and has been shown to have antioxidant properties. Neural precursor cells, a cell population of considerable interest as a source of cells for neural tissue regeneration strategies, generate a high amount of reactive oxygen species, and when associated with a degradable biomaterial, may be impacted by released lactic acid. In this work, the effect of lactic acid on a neural cell population containing proliferative neural precursor cells was examined in monolayer culture. Lactic acid was found to scavenge exogenously added free radicals produced in the presence of either hydrogen peroxide or a photoinitiator (I2959) commonly utilized in the preparation of photopolymerizable biomaterials. In addition to its effect on exogenously added free radicals, lactic acid reduced intracellular redox state, increased the proliferation of the cell population, and modified the cell composition. The findings of this study provide insight into the role that lactic acid plays naturally on developing neural cells and are also of interest to biomaterials scientists that are focused on the development of degradable lactic‐acid‐based polymers for cell culture devices. The effect of lactic acid on other cell populations may differ and should be characterized to best understand how cells function in degradable cell culture devices. Biotechnol. Bioeng. 2009;103: 1214–1223. © 2009 Wiley Periodicals, Inc.     

Insight into the bovine milk peptide LPcin‐YK3 selection in the proteolytic system of Lactobacillus species

Antimicrobial peptides are class of small, positively charged peptides known for their broad‐spectrum antimicrobial activity. Antimicrobial activities for most antimicrobial peptides have largely remained elusive, particularly in the lactic acid bacteria. However, recently our investigation using LPcin‐YK3, an antimicrobial peptide from bovine milk, suggests that in vitro antimicrobial activity was reduced over 100‐fold compared with pathogenic bacteria. Additionally, for the structural study of how antimicrobial peptide undergoes its reaction at the proteolytic pathway of lactic acid bacteria based on degradation assay and propidium iodide staining, we performed molecular docking for interaction between oligopeptide‐binding protein A and LPcin‐YK3 peptide. Given that degradation related to the LPcin‐YK3 peptide in lactic acid bacteria proteolytic system, the inhibitory inactivity of LPcin‐YK3 against beneficial lactic acid bacteria strains may be one of the primary pharmacological properties of recombinant peptide discovered in bovine milk. These results provide structural and functional insights into the proteolytic mechanism and possibility as a putative substrate of oligopeptide‐binding protein A in respect of LPcin‐YK3 peptide.     

硬蜱哈氏器嗅觉功能的研究

研究了五种硬蜱的哈氏器在不同虫期(若虫和成虫)和不同营养状态(饱或饿)对不同浓度的弱酸、弱碱以及对低温刺激的电生理反应.此外,比较了四种硬蜱成虫对五种驱避剂的行为反应.结果表明,硬蜱哈氏器能够感受氨和醋酸蒸气的刺激,反应的相对强度在一定范围内随蒸气浓度而变化.哈氏器还能感受温度的变化.从行为反应见到驱避剂对不同种类硬蜱的驱避强度不同,每种蜱对不同药物的敏感性也不同.截肢试验证明哈氏器是驱避剂的感受器.     

Technologically important properties of lactic acid bacteria isolates from Beyaz cheese made from raw ewes'' milk

AIMS: The aim of the study was to characterize isolates of lactic acid bacteria from Beyaz cheese and to study some of their technologically important properties. METHODS AND RESULTS: Seventy-seven lactic acid bacteria isolated from Beyaz, a Turkish white-brined cheese made from raw ewes' milk without any starter, were classified by phenotypic criteria and sodium dodecyl sulphate-polyacrylamide gel electrophoresis of whole-cell proteins. Whole cells of Lactococcus lactis subsp. lactis and enterococci showed lipolytic and proteolytic activities. Strains were found that differed in terms of their acidifying and caseinolytic activity. Most of the enterococci isolates showed tyrosine decarboxylase activity; moreover, lactobacilli exhibited weak antibacterial activities against foodborne pathogens. CONCLUSIONS: Strains of lactic acid bacteria with interesting biotechnologically important properties may be found in Beyaz cheese. SIGNIFICANCE AND IMPACT OF THE STUDY: Lactic acid bacteria isolates with interesting biotechnological profiles may influence the quality and variety of dairy products, if they are used as starters, and their cheese-making characteristics seem promising.     

Cell engineering biointerface focusing on cytocompatibility using phospholipid polymer with an isomeric oligo(lactic acid) segment

Initial contact between a biological environment and a biomaterial ultimately decides the in vivo performance. Therefore, the fabrication of a delicate biointerface is important because it can be utilized as a platform for novel biomaterials. For the preparation of advanced biomedical devices such as biochips, nanoparticles, and cell engineering devices, the surface properties may be modified by the design of polymeric biomaterials. Anomalous phospholipid polymers with an isomeric oligo(lactic acid) segment were designed and evaluated as a biointerface. The phospholipid polymer containing 2-methacryloyloxyethyl phosphorylcholine was easily copolymerized with isomeric oligo(lactic acid) macromonomers, and the obtained polymer could easily form thin coating membranes as biointerfaces. The oligo(lactic acid) involves three kinds of isomers: dl-, d-, and l-forms. The favorable characteristic on the surface provides regulation of cell-material interactions on the biointerface. The oligo(lactic acid) segment could form hydrophobic domains, which were considered to be located on the interface, to enhance protein adsorption and cell adhesion. The most favorable characteristics on the biointerface were dual functions of cytocompatibility by the phospholipid polymer and cell adhesion property by the oligo(lactic acid) segment. In this study, we focused on the biological responses such as protein adsorption and cell adhesion by change in the oligo(lactic acid) component. The cell viability on the confluent stage was evaluated in terms of metabolic activity.     

Olfactory responses of the antennal trichoid sensilla to chemical repellents in the mosquito, Culex quinquefasciatus

Insect repellents are widely used to protect against insect bites and thus prevent allergic reaction and the spread of disease. To gain insight into the mosquito’s response to chemicals repellents, we investigated the interaction between the olfactory system of the mosquito Culex quinquefasciatus Say and chemical repellents using single sensillum recording. The interactions of 50 repellent chemicals with olfactory receptor neurons were measured in six different types of mosquito sensilla: long sharp trichoid (LST), short sharp trichoid (SST), short blunt trichoid I (SBT-I), short blunt trichoid II (SBT-II), short blunt trichoid-curved (SBT-C), and grooved peg (GP). A single olfactory neuron reacted to the chemical repellents in each of the sensilla except for SBT-I and SBT-II, where two neurons were involved. Other than LST and GP, which showed no or very weak responses to the repellents tested, all the sensilla showed significant excitatory responses to certain types of repellents. Terpene-derived chemicals such as eucalyptol, α-pinene, and camphor, stimulated olfactory receptor neurons in a dose-dependent manner and mosquitoes responded more strongly to terpene-derived chemical repellents than to non-terpene-derived chemicals such as dimethyl phthalate. Mosquitoes also exhibited a similar response to stereoisomers of chemicals such as (−)-β-pinene versus (+)-β-pinene, and (−)-menthone versus (+)-menthone. This study not only demonstrates the effects of chemical repellents on the mosquito olfactory system but also provides important information that will assist those screening new mosquito repellents and designing new mosquito control agents.     

蚊虫搜寻吸血寄主和产卵行为的调节因子及相关嗅觉机理

嗅觉在蚊虫的吸血寄主搜寻、产卵和糖源搜寻行为中起决定作用,而在交配行为中的作用并不清楚。本文系统全面地综述了近20年来蚊虫化学生态学和嗅觉识别的分子机理的研究。蚊虫的触角、下颚须和口喙上的嗅觉感器感觉环境中释放的各种挥发性化合物。气味分子与嗅觉气味结合蛋白和气味受体的结合所启动的一系列生化反应产生神经动作电位。蚊虫嗅觉神经元编码气味中化合物的组成、浓度及其暂时瞬间的浓度变化和空间分布。吸血前后神经元的活性在数量和质量上有变化,反映了蚊虫在搜寻吸血寄主和产卵行为上的调节。在吸血寄主搜寻中,人体和动物释放的二氧化碳、乳酸以及其他气味协同引诱蚊虫向目标气味源定向飞行,最后找到吸血寄主。而成熟产卵雌蚊是利用产卵场所释放的腐烂气味寻找适宜的产卵场所,一些蚊虫卵、幼虫或蛹分泌的产卵信息素引诱和刺激雌蚊产卵,并与产卵生境气味起协同作用。植物气味尤其是花香味引诱蚊虫找到蜜源。驱避剂也是直接或间接通过嗅觉起作用,一些驱蚊剂由于阻断嗅觉反应而抑制蚊虫的定向飞行。从植物、动物或人体以及产卵场所释放的气味中有望找到有效的引诱和驱避化合物。对蚊虫嗅觉识别机理的认识将使我们开发出有效的蚊虫诱捕技术,进而应用于种群监测和控制。     

转运蛋白提高凝结芽孢杆菌酸耐受性

光学纯乳酸作为可降解生物材料——聚乳酸(polylactic acid,PLA)的前体物质,正在受到广泛关注。乳酸发酵过程中酸性产物的积累会影响菌株的生长,提高菌株酸耐受性具有重要意义。本研究以乳酸生产菌株凝结芽孢杆菌(Bacillus coagulans) DSM1为出发菌株,通过对凝结芽孢杆菌DSM1及其乳酸脱氢酶双敲除菌株(DldhL1DldhL2)进行比较转录分析,筛选酸耐受相关的转运蛋白基因。对关键基因RS16330、RS06895、RS16325、RS10595、RS00500、RS07275、RS10635及RS01930进行实时定量PCR分析,发现基因RS06895、RS10595、RS00500和RS10635在发酵12 h和24 h转录水平显著增强。过表达RS10595基因的菌株,在中性(pH 6.0)条件下生长状况和发酵性能均受到抑制,但在酸性条件下(pH 4.6),其乳酸生成相比对照组显著提高。上述结果表明,RS10595基因与菌株DSM1的酸耐受性密切相关。本研究有助于进一步探究凝结芽孢杆菌酸耐受的机制,也为构建耐酸菌株提供了基础。     

Efficacy of lactic acid against Listeria monocytogenes attached to poultry skin during refrigerated storage

AIMS: The aim of this study was to evaluate the effect of lactic acid washing on the growth of Listeria monocytogenes on poultry legs stored at 4 degrees C for 7 days. METHODS AND RESULTS: Fresh inoculated chicken legs were dipped into either a 0.11, 0.22 mol l(-1) or 0.55 mol l(-1) lactic acid solution for 5 min or distilled water (control). Surface pH values, sensorial characteristics and L. monocytogenes, mesophiles and pychrotrophs counts were evaluated after treatment (day 0) and after 1, 3, 5 and 7 days of storage at 4 degrees C. Legs washed with 0.55 mol l(-1) lactic acid for 5 min showed a significant (P < 0.05) inhibitory effect on L. monocytogenes compared with control legs, being about 1.74 log units lower in the first ones than in control legs after 7 days of storage. Sensory quality was not adversely affected by lactic acid, with the exception of colour. CONCLUSIONS: Treatments with 0.55 mol l(-1) lactic acid reduced bacterial growth and preserved reasonable sensorial quality after storage at 4 degrees C for 7 days. However, it was observed a reduction in the colour score within 1 day post-treatment with 0.55 mol l(-1) lactic. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrates that, while lactic acid did reduce populations of L. monocytogenes on poultry, it did not completely inactivate the pathogen. The application of lactic acid may be used as an additional hurdle contributing to extend the shelf-life of raw poultry.     

Reactive extraction of lactic acid using alamine 336 in MIBK: equilibria and kinetics

Lactic acid is an important commercial product and extracting it out of aqueous solution is a growing requirement in fermentation based industries and recovery from waste streams. The design of an amine extraction process requires (i) equilibrium and (ii) kinetic data for the acid-amine (solvent) system used. Equilibria for lactic acid extraction by alamine 336 in methyl-iso-butyl-ketone (MIBK) as a diluent have been determined. The extent to which the organic phase (amine +MIBK) may be loaded with lactic acid is expressed as a loading ratio, z=[HL](o)/[B](i,o). Calculations based on the stoichiometry of the reactive extraction and the equilibria involved indicated that more lactic acid is transferred to the organic phase than would be expected from the (1:1) stoichiometry of the reaction. The extraction equilibrium was interpreted as a result of consecutive formation of two acid-amine species with stoichiometries of 1:1 and 2:1. Equilibrium complexation constant for (1:1) and (2:1) has been estimated. Kinetics of extraction of lactic acid by alamine 336 in MIBK has also been determined. In a first study of its kind, the theory of extraction accompanied by a chemical reaction has been used to obtain the kinetics of extraction of lactic acid by alamine 336 in MIBK. The reaction between lactic acid and alamine 336 in MIBK in a stirred cell falls in Regime 3, extraction accompanied by a fast chemical reaction occurring in the diffusion film. The reaction has been found to be zero order in alamine 336 and first order in lactic acid with a rate constant of 1.38 s(-1). These data will be useful in the design of extraction processes.