Enantioseparation of mandelic acid on vancomycin column: Experimental and docking study

So far, no detailed view has been expressed regarding the interactions between vancomycin and racemic compounds including mandelic acid. In the current study, a chiral stationary phase was prepared by using 3-aminopropyltriethoxysilane and succinic anhydride to graft carboxylated silica microspheres and subsequently by activating the carboxylic acid group for vancomycin immobilization. Characterization by elemental analysis, Fourier transform infrared spectroscopy, solid-state nuclear magnetic resonance, and thermogravimetric analysis demonstrated effective functionalization of the silica surface. R and S enantiomers of mandelic acid were separated by the synthetic vancomycin column. Finally, the interaction between vancomycin and R/S mandelic acid enantiomers was simulated by Auto-dock Vina. The binding energies of interactions between R and S enantiomers and vancomycin chiral stationary phase were different. In the most probable interaction, the difference in mandelic acid binding energy was approximately 0.2 kcal/mol. In addition, circular dichroism spectra of vancomycin interacting with R and S enantiomers showed different patterns. Therefore, R and S mandelic acid enantiomers may occupy various binding pockets and interact with different vancomycin functions. These observations emphasized the different retention of R and S mandelic acid enantiomers in vancomycin chiral column.     

Sublethal effects of chronic exposure to chlorpyrifos or imidacloprid insecticides or their binary mixtures on Culex pipiens mosquitoes

Mosquitoes represent one of the most significant threats to human and veterinary health throughout the world. Consequently, improving strategies for the control of mosquitoes is essential. In the present study, juvenile Culex pipiens (Diptera: Culicidae), the common house mosquito, are chronically exposed to sublethal concentrations of chlorpyrifos (20% of LC₅₀) and imidacloprid (5% of LC₅₀), both separately and as a mixture. Developmental time, the emergence rate of adults and the expression of five selected genes involved in detoxification and resistance to pesticides are assessed. To assess the effects on oviposition choice, gravid females are forced to oviposit into cups containing water with added chlorpyrifos, imidacloprid or a mixture of both. The time required for the development of second‐ and third‐instar larvae is observed to differ significantly between treatments. Adults of C. pipiens fail to emerge from larvae hatched in both imidacloprid and the binary mixture. The expression of the four quantified detoxification genes differs significantly in third‐larval instars exposed to chlorpyrifos and/or imidacloprid compared with controls. Gravid females also fail to lay eggs on water to which either of the insecticides or the binary mixture is added, although they do lay eggs in cups containing water only. Chronic exposure to sublethal concentrations of chlorpyrifos or imidacloprid has significant adverse effects on development and thus the reproductive fitness of C. pipiens and, accordingly, could be used in the population control of these mosquitoes.     

Larvicidal effects of some natural products on the Aedes aegypti mosquito,a vector of dengue fever and Zika virus

Natural products are considered a good choice in the biological control of mosquitoes because they are an effective way to eliminate larvae and prevent an increase in mosquito numbers, while simultaneously not polluting the environment or damaging health. This investigation was designed to study the potential toxicity of three species of algae, Caulerpa racemosa (Weber-van Bosse, 1909), Padina boryana (Thivy, 1966), and Turbinaria ornata (Turner J. Agardh, 1848), on the larvae of Aedes aegypti mosquito, the vector of dengue and Zika viruses. Among the studied species, Caulerpa racemosa showed the greatest effectiveness in eradicating A. aegypti larvae with an LC₅₀ = 43.5 ppm, followed by Padina boryana with an LC₅₀ = 51.93 ppm. Both species proved to be excellent candidates as a source of larvicidal agents and could be used commercially in mosquito control programs as eco-friendly biopesticides. The combined activity of different mixtures against mosquito larvae was expressed as the coeffective factor (C.F.). C.F. values showed that the joint activity of insect growth regulator Dudim in combination with Caulerpa racemosa and Padina boryana extracts produced degrees of potentiation effects and degrees of additive effects were obtained with Dudim in combination with Turbinaria ornata extract.     

Effects of artificial feeding on aggressive behaviour of rhesus monkeys in India

Artificial feeding of rhesus monkeys (Macaca mulatta), which provides the major food source for most rhesus groups in rural and urban habitats, is common practice in India. Such feeding results in significant increases in aggressive competition within the monkey groups: during feeding periods the frequencies of aggressive threats, chases, and attacks increased two to six times above those of non-feeding periods in each of eight different groups. Fighting behaviour did not increase in most groups studied, but did show a rise in one large urban group in Calcutta. The implications of these results for the management of primate breeding colonies are discussed.