Adulticidal properties of synthesized silver nanoparticles using leaf extracts of Feronia elephantum (Rutaceae) against filariasis,malaria, and dengue vector mosquitoes

Mosquito-borne diseases with an economic impact create loss in commercial and labor outputs, particularly in countries with tropical and subtropical climates. Mosquito control is facing a threat because of the emergence of resistance to synthetic insecticides. Extracts from plants may be alternative sources of mosquito control agents because they constitute a rich source of bioactive compounds that are biodegradable into nontoxic products and potentially suitable for use to control mosquitoes. Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. In view of the recently increased interest in developing plant origin insecticides as an alternative to chemical insecticide, in the present study, the adulticidal activity of silver nanoparticles (AgNPs) synthesized using Feronia elephantum plant leaf extract against adults of Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus was determined. The range of concentrations of synthesized AgNPs (8, 16, 24, 32, and 40 μg mL^?1) and aqueous leaf extract (40, 80, 120, 160, and 200 μg mL^?1) were tested against the adults of A. stephensi, A. aegypti, and C. quinquefasciatus. Adults were exposed to varying concentrations of aqueous crude extract and synthesized AgNPs for 24 h. Considerable mortality was evident after the treatment of F. elephantum for all three important vector mosquitoes. The synthesized AgNPs from F. elephantum were highly toxic than crude leaf aqueous extract to three important vector mosquito species. The results were recorded from UV–visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy analysis (EDX), and transmission electron microscopy (TEM). Synthesized AgNPs against the vector mosquitoes A. stephensi, A. aegypti, and C. quinquefasciatus had the following lethal dose (LD)₅₀ and LD₉₀ values: A. stephensi had LD₅₀ and LD₉₀ values of 18.041 and 32.575 μg mL^?1; A. aegypti had LD₅₀ and LD₉₀ values of 20.399 and 37.534 μg mL^?1; and C. quinquefasciatus had LD₅₀ and LD₉₀ values of 21.798 and 39.596 μg mL^?1. No mortality was observed in the control. These results suggest that the leaf aqueous extracts of F. elephantum and green synthesis of AgNPs have the potential to be used as an ideal eco-friendly approach for the control of the A. stephensi, A. aegypti, and C. quinquefasciatus. This is the first report on the adulticidal activity of the plant extracts and AgNPs.     

Low-cost and eco-friendly green synthesis of silver nanoparticles using Feronia elephantum (Rutaceae) against Culex quinquefasciatus,Anopheles stephensi,and Aedes aegypti (Diptera: Culicidae)

Mosquitoes transmit serious human diseases, causing millions of deaths every year. The use of synthetic insecticides to control vector mosquitoes has caused physiological resistance and adverse environmental effects in addition to high operational cost. Insecticides of synthesized natural products for vector control have been a priority in this area. In the present study, the larvicidal activity of silver nanoparticles (AgNPs) synthesized using Feronia elephantum plant leaf extract against late third-instar larvae of Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus was determined. The range of concentrations of synthesized AgNPs (5, 10, 15, 20, and 25 μg mL^?1) and aqueous leaf extract (25, 50, 75, 100, and 125 μg mL^?1) were tested against the larvae of A. stephensi, A. aegypti, and C. quinquefasciatus. Larvae were exposed to varying concentrations of aqueous crude extract and synthesized AgNPs for 24 h. Considerable mortality was evident after the treatment of F. elephantum for all three important vector mosquitoes. The synthesized AgNPs from F. elephantum were highly toxic than crude leaf aqueous extract to three important vector mosquito species. The results were recorded from UV–visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy analysis (EDX). Synthesized AgNPs against the vector mosquitoes A. stephensi, A. aegypti, and C. quinquefasciatus had the following LC₅₀ and LC₉₀ values: A. stephensi had LC₅₀ and LC₉₀ values of 11.56 and 20.56 μg mL^?1; A. aegypti had LC₅₀ and LC₉₀ values of 13.13 and 23.12 μg mL^?1; and C. quinquefasciatus had LC₅₀ and LC₉₀ values of 14.19 and 24.30 μg mL^?1. No mortality was observed in the control. These results suggest that the green synthesis of silver nanoparticles using F. elephantum has the potential to be used as an ideal eco-friendly approach for the control of A. stephensi, A. aegypti, and C. quinquefasciatus. This is the first report on the mosquito larvicidal activity of the plant extracts and synthesized nanoparticles.     

In vitro and in vivo antiplasmodial activity of the root extracts of Brucea mollis Wall. ex Kurz

Malaria control is compromised worldwide by continuously evolving drug-resistant strains of the parasite demanding exploration of natural resources for developing newer antimalarials. The northeastern region of India is endemic for malaria characterized by high prevalence of drug-resistant Plasmodium falciparum strains. Many plants are used by the indigenous communities living in the northeast India in their traditional system of medicine for the treatment of malarial fever. Folklore claim of antimalarial property of one such plant Brucea mollis was evaluated in vitro and in vivo for antiplasmodial activity. Crude extracts from dried B. mollis root powder were prepared through soxhlet extraction using petroleum ether, methanol, and water sequentially. Methanol extract was further partitioned between chloroform and water. These extracts were tested in vitro against laboratory-adapted chloroquine-sensitive and chloroquine-resistant strains of P. falciparum. In in vitro evaluation, extracts were found more active on the chloroquine-sensitive strain. Methanolic-chloroform (IC₅₀ 5.1 μg?ml^?1) and methanolic-aqueous (IC₅₀ 13.9 μg?ml^?1) extracts recorded significant in vitro antiplasmodial activity which was also supported by their promising in vivo activity (ED₅₀ 72 and 30 mg?kg^?1?bw?day^?1, respectively) against chloroquine-resistant Plasmodium yoelli N-67 strain in Swiss albino mice. Methanolic-aqueous extract-treated mice survived on average for 14 days that was comparable to the reference drug chloroquine. This is the first report of antiplasmodial activity of B. mollis validating the traditional use of this plant as antimalarial in the northeast India and calls for further detailed investigations.     

Development of an antibody-based colloidal gold immunochromatographic lateral flow strip test for natamycin in milk and yoghurt samples

An immunochromatographic lateral flow strip test was developed for the detection of natamycin (Nata) residues in milk and cheese samples. Monoclonal antibody (mAb) against Nata was produced with a half maximal inhibitory concentration of 1.85?μg?L^?1. MAb conjugated with gold nanoparticles was the detection reagent. Nata conjugated with ovalbumin via the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide method immobilized on a nitrocellulose membrane was the capture reagent. This semi-quantitative method required only 15?min to complete. The optimum concentrations of coating antigen and mAb were 0.15?µg?mL^?1 and 0.2?µg?mL^?1, respectively. Based on an optical density scanner, the visual limit of detection of Nata was 5?μg?L^?1 and 10?μg?kg^?1 in milk and yoghurt samples, respectively.     

Evaluation of plant-mediated synthesized silver nanoparticles against vector mosquitoes

Diseases transmitted by blood-feeding mosquitoes, such as dengue fever, dengue hemorrhagic fever, Japanese encephalitis, malaria, and filariasis, are increasing in prevalence, particularly in tropical and subtropical zones. To control mosquitoes and mosquito-borne diseases, which have worldwide health and economic impacts, synthetic insecticide-based interventions are still necessary, particularly in situations of epidemic outbreak and sudden increases of adult mosquitoes. Green nanoparticle synthesis has been achieved using environmentally acceptable plant extract and eco-friendly reducing and capping agents. In view of the recently increased interest in developing plant origin insecticides as an alternative to chemical insecticide, in the present study, the adulticidal activity of silver nanoparticles (AgNPs) synthesized using Heliotropium indicum plant leaf extract against adults of Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus was determined. Adult mosquitoes were exposed to varying concentrations of aqueous extract of H. indicum and synthesized AgNPs for 24 h. AgNPs were rapidly synthesized using the leaf extract of H. indicum, and the formation of nanoparticles was observed within 6 h. The results recorded from UV–vis spectrum, Fourier transform infrared, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy support the biosynthesis and characterization of AgNPs. The maximum efficacy was observed in synthesized AgNPs against the adult of A. stephensi (lethal dose (LD)₅₀?=?26.712 μg/mL; LD₉₀?=?49.061 μg/mL), A. aegypti (LD₅₀?=?29.626 μg/mL; LD₉₀?=?54.269 μg/mL), and C. quinquefasciatus (LD₅₀?=?32.077 μg/mL; LD₉₀?=?58.426 μg/mL), respectively. No mortality was observed in the control. These results suggest that the leaf aqueous extracts of H.indicum and green synthesis of AgNPs have the potential to be used as an ideal eco-friendly approach for the control of the A. stephensi, A. aegypti, and C. quinquefasciatus. This is the first report on the adulticidal activity of the plant extracts and AgNPs.     

Gastrointestinal response and endotoxemia during intense exercise in hot and cool environments

This study investigated plasma lipopolysaccharides (LPS) concentration and intestinal permeability after 60-min run at 70 % maximum oxygen uptake (VO_2max) in hot [33 °C, 50 % relative humidity (rH)] and cool (22 °C, 62 % rH) conditions. Fifteen volunteers gave their informed consent to participate in this study. Their venous blood samples were taken before, after, 2 and 5 h after exercise in each of the conditions. The order of the two environmental conditions in which they exercised in was randomised and counterbalanced. Plasma LPS concentration increased by an average of 54.0 % (95 % confidence interval: 30.7, 75.1 %) after exercising in the hot trial but no significant changes were observed in cool trial, where mean plasma LPS concentration was 12.0 ± 6.4 pg mL^?1 (before), 10.9 ± 5.4 pg mL^?1 (after), 10.7 ± 6.0 pg mL^?1 (2 h after) and 10.6 ± 5.7 pg mL^?1 (5 h after). Median (range) plasma claudin-3 (CLDN3) concentration was significantly higher after exercise (hot: 8.2 [1.0–13.0] ng mL^?1 and cool: 7.6 [0.6–13.4] ng mL^?1) as compared to before exercise (hot: 6.6 [0.7–11.8] ng mL^?1 and cool: 6.7 [0.8–12.6] ng mL^?1) (p < 0.05), but there is no significant difference observed between trials (p > 0.05). Changes in intestinal permeability are only affected by exercise while exercise-induced endotoxemia is affected by environmental conditions. This study, thus, highlights that an increase in intestinal permeability is not sufficient to trigger exercise-induced endotoxemia, suggesting that post-LPS translocation events may have a greater impact in its occurrence.     

Acaricide activity in vitro of Acmella oleracea against Rhipicephalus microplus

Cattle tick control has been limited by the resistance of these parasites to synthetic acaricides. Natural products are a possible alternative as they have different mechanisms of action. Acmella oleracea is a native plant with a large cultivated area in the Amazon region and could be easily used for large-scale preparation of a commercial product. This study evaluated the in vitro action of the hexane extract of the aerial parts of A. oleracea on larvae and engorged females of the cattle tick Rhipicephalus microplus. Spilanthol was the major constituent with a content of 14.8 % in the extract. The hexane extract of A. oleracea was highly effective against larvae of R. microplus with an LC₅₀ of 0.8 mg mL^?1. Against engorged females, hexane extract of A. oleracea reduced oviposition and hatchability of eggs with an LC₅₀ of 79.7 mg mL^?1. Larvae and engorged females were killed by the hexane extract with high efficiency (>95 %) at concentrations of 3.1 and 150.0 mg mL^?1, respectively. These results demonstrate that the hexane extract of A. oleracea has significant activity against R. microplus and has potential to be developed into formulations for tick control.     

Bioactivity of Dianthus caryophyllus, Lepidium sativum, Pimpinella anisum, and Illicium verum essential oils and their major components against the West Nile vector Culex pipiens

Mosquitoes constitute a severe health problem in many areas all over the world. There are many regions of the tropics and subtropics where mosquitoes are one of the main reasons for inhibiting the economic upgrade. Except nuisance, their medical importance is another matter of attention since mosquitoes are vectors for a wide variety of vector-borne diseases. Due to disadvantages of currently used chemical control methods, it is unavoidable to search for eco-friendly new molecules. We report herein the evaluation of the larvicidal effect exhibited by essential oils of Dianthus caryophyllus, Lepidium sativum, Pimpinella anisum, and Illicium verum against late third to early fourth instar mosquito larvae of Culex pipiens. Furthermore, phytochemical analysis of plant samples revealed their major compounds to be β-caryophyllene, eugenol, eucalyptol, α-terpinyl acetate, and (E)-anethole which were also tested for their potential larvicidal activity. For D. caryophyllus and L. sativum, this was the first report on the chemical composition of their essential oils. The essential oils of I. verum and P. anisum demonstrated high larvicidal activity with a LC₅₀ <18 mgL^?1. The other two essential oils of D. caryophyllus and L. sativum revealed moderate larvicidal activity, displaying a LC₅₀ value above 50 mgL^?1. Among the pure components, the most toxic were eugenol, (E)-anethole, and α-terpinyl acetate, with LC₅₀ values 18.28, 16.56, and 23.03 mgL^?1, respectively. Eucalyptol (1,8 cineole) and β-caryophyllene were inactive at concentrations even as high as 100 mgL^?1, showing the least significant activity against mosquito larvae. Results allow some rationalization on the relative importance of the major compounds regarding the larvicidal activity of selected essential oils and their potential use as vector control agents.     

Essential oil composition, adult repellency and larvicidal activity of eight Cupressaceae species from Greece against Aedes albopictus (Diptera: Culicidae)

The present study evaluated leaf essential oils from eight Cupresaceae species; Cupressus arizonica, Cupressus benthamii, Cupressus macrocarpa, Cupressus sempervirens, Cupressus torulosa, Chamaecyparis lawsoniana, Juniperus phoenicea, and Tetraclinis articulata for their larvicidal and repellent properties against Aedes albopictus, a mosquito of great ecological and medical importance. Based on the LC₅₀ values, C. benthamii essential oil was the most active (LC₅₀?=?37.5 mg/L) while the other tested Cupressaceae essential oils provided rather moderate toxicity against larvae (LC₅₀?=?47.9 to 70.6 mg/L). Under the used laboratory conditions, three of the essential oils (C. benthamii, C. lawsoniana, and C. macrocarpa) provided sufficient protection against mosquito adults, equivalent to the standard repellent “Deet” in the 0.2 mg/cm² dose, while C. macrocarpa assigned as the superior repellent oil in the 0.08 mg/cm² dose. Chemical analysis of the essential oils using gas chromatography and gas chromatography–mass spectrometry revealed the presence of 125 components.     

Screening of plant extracts for anthelmintic activity against Dactylogyrus intermedius (Monogenea) in goldfish (Carassius auratus)

With the aim of finding natural anthelmintic agents against Dactylogyrus intermedius (Monogenea) in goldfish (Carassius auratus), 26 plants were screened for antiparasitic properties using in vivo anthelmintic efficacy assay. The results showed that Caesalpinia sappan, Lysima chiachristinae, Cuscuta chinensis, Artemisia argyi, and Eupatorium fortunei were found to have 100 % anthelmintic efficacy at 125, 150, 225, 300, and 500 mg L^?1 after 48 h of exposure. Crude extract of the five plants were further partitioned with petroleum ether, chloroform, ethyl acetate, methanol, and water to obtain anthelmintically active fractions with various polarity. Among these fractions tested, the ethyl acetate extract of L. chiachristinae was found to be the most effective with a 50 % effective concentration (EC₅₀) value of 5.1 mg/L after 48 h of exposure. This was followed by ethyl acetate extract of C. chinensis (48 h-EC₅₀?=?8.5 mg L^?1), chloroform extracts of C. sappan (48 h-EC₅₀?=?15.6 mg L^?1), methanol extract of C. chinensis (48 h-EC₅₀?=?15.9 mg L^?1), and chloroform and petroleum ether extract of L. chiachristinae (EC₅₀ values of 17.2 and 21.1 mg/L, respectively), suggesting that these plants, as well as the active fractions, provide potential sources of botanic drugs for the control of D. intermedius in aquaculture.     

Chemical composition and acaricidal activity of essential oil from Lippia sidoides on larvae of Dermacentor nitens (Acari: Ixodidae) and larvae and engorged females of Rhipicephalus microplus (Acari: Ixodidae)

The aim of this work was to identify the compounds and to investigate the acaricidal activity of the essential oil from the leaves of Lippia sidoides on Rhipicephalus microplus and Dermacentor nitens. The oil was obtained by hydrodistillation and analyzed by gas chromatography (GC/FID) and gas chromatography/mass spectrometry. In total, 15 compounds comprising 99.97 % of the total peak area were identified. The main constituent of the essential oil was thymol (67.60 %). The acaricidal activity was assessed by the modified larval packet test, with oil concentrations of 2.5, 5.0, 10.0, 15.0, and 20.0 μl/ml, and by the female immersion test with concentrations of 10.0, 20.0, 40.0, 60.0, and 80.0 μl/ml. The mortality of the R. microplus and D. nitens larvae was greater than 95 % starting at concentrations of 10.0 and 20.0 μl/ml, respectively. In the test with the engorged females, the L. sidoides essential oil starting at a concentration of 40.0 μl/ml caused a significant reduction (p?<?0.05) in the values of the egg mass weight and egg production index. The viability of the eggs was affected in all the treated groups, with significantly lower hatching rates (p?<?0.05) in relation to the control group. The control percentages at concentrations of 10.0, 20.0, and 30.0 μl/ml were 54, 57, and 72 %, and reached 100 % at the highest two concentrations (60.0 and 80.0 μl/ml). Therefore, it can be concluded that the essential oil from the leaves of L. sidoides has acaricidal activity on R. microplus and D. nitens.     

In vitro antiplasmodial activity of some medicinal plants of Burkina Faso

Malaria remains a major public health problem due to the emergence and spread of Plasmodium falciparum drug resistance. There is an urgent need to investigate new sources of antimalarial drugs which are more effective against Plasmodium falciparum. One of the potential sources of antimalarial drugs is traditional medicinal plants. In this work, we studied the in vitro antiplasmodial activity of chloromethylenic, methanolic, and MeOH/H₂O (1/1) crude extracts and decoction obtained from eight medicinal plants collected in Burkina Faso and of total alkaloids for five plants. Extracts were evaluated in vitro for efficacy against Plasmodium falciparum strain K1, which is resistant to chloroquine, pyrimethamine and proguanil using the fluorescence-based SYBR Green I assay. The antiproliferative activity on human-derived hepatoma cell line HepG2 and Chinese hamster ovary (CHO) cells was evaluated using the 3-[4,5-dimethylthyazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) test in order to determine the selectivity index. Among the plant extracts tested for in vitro antiplasmodial activity, 16 were considered to be inactive (with IC₅₀?>?10 μg/ml), six showed a moderate activity (5?<?IC₅₀?≤?10 μg/ml), and six were found to have a good in vitro activity with IC₅₀ value?≤?5 μg/ml. The highest antiplasmodial activity was found for extracts from: the alkaloid leaf extract and the chloromethylenic extracts of Combretum fragrans (IC₅₀?=?3 μg/ml, IC₅₀?=?5 μg/ml), the total alkaloids and the chloromethylenic leaf extracts of Combretum collinum (IC₅₀?=?4 μg/ml), the MeOH/H₂O leaf extract of Terminalia avicennioides (IC₅₀?=?3.5 μg/ml), and the alkaloid leaf extract of Pavetta crassipes (IC₅₀?=?5 μg/ml). Three other extracts showed moderate antiplasmodial activity (5?<?IC₅₀?≤?10 μg/ml): Terminalia avicennioides and Combretum fragrans methanolic extracts and Acacia kirkii alkaloid leaf extract (IC₅₀?=?6.5, 9 and 10 μg/ml respectively). The Terminalia avicennioides crude MeOH/H₂O (80:20 v/v) extract of the leaves was submitted to a successive liquid/liquid extraction with ethylacetate and n-butanol respectively. The extracts were investigated for in vitro antiplasmodial activity and antioxidant properties using DPPH^●, ABTS⁺ and FRAP methods. The ethylacetate extract showed the best antiplasmodial activity (7 μg/ml) and the active constituent was isolated as ellagic acid by bioguided fractionation with an IC₅₀?=?0.2 μM on Plasmodium falciparum and SI?=?152. Besides, Terminalia avicennioides leaf extract and ellagic acid showed a good antioxidant activity. Our finding confirms the importance of investigating the antimalarial activity of plant species used in traditional medicine. Overall, two plants belonging to the Combretaceae family, Combretum fragrans and Combretum collinum appeared to be the best candidates and will be further investigated for their antiplasmodial properties, in order to isolate the molecules responsible for the antiplasmodial activity.     

The anti-parasitic effects of Nicotina tabacum on leeches

In this study, we evaluated the potential use of Nicotina tabacum in controlling leech populations. After treating the leeches with different concentrations of N. tabacum for 30 min, the LC₅₀ values were analysed. Copper sulphate and ammonium chloride were used as positive controls. The anti-parasitic effect of N. tabacum was compared with positive controls. Our data showed that the LD₅₀ values for N. tabacum were 13?×?10⁴ ppm which was considerable compared with positive control. Our finding offers an opportunity for using the plant for anti-parasite purposes.     

Evaluation of bioefficacy of three Citrus essential oils against the dengue vector Aedes albopictus (Diptera: Culicidae) in correlation to their components enantiomeric distribution

Laboratory experiments were conducted to study the bioefficacy against Ae. albopictus of three Citrus essential oils, derived from peels of Citrus sinensis, Citrus limon, and Citrus paradise and of their components. Chiral gas chromatography analysis revealed the dominant occurrence of R-(+)-limonene and (?)-??-pinene in all three essential oils while in the case of lemon oil ??-terpinene, neral, and geranial detected also among other components. The tested Citrus essential oils were toxic against mosquito larvae with LC₅₀ values ranging from 25.03 to 37.03?mg?l^?1. Among citrus essential oils components tested, ??-terpinene was the most toxic (LC₅₀?=?20.21?mg?l^?1) followed by both enantiomeric forms of limonene (LC₅₀?=?35.99 and 34.89?mg?l^?1, for R-(+)-limonene and S-(?)-limonene, respectively). The delayed toxic effects after exposure of larvae to sublethal (LC₅₀) doses were also investigated for citrus essential oils and their major component R-(+)-limonene, indicating a significant reduction of pupal survival. In repellent bioassays, lemon essential oil, S-(?)-limonene, citral (mixture of neral\geranial) and (+)-??-pinene were the most effective compared with other citrus essential oils and components against adult mosquitoes. Repellent bioassays also revealed that limonenes and ??-pinenes showed an isomer dependence repellent activity. Finally, according to enantiomeric distribution of limonene and ??- and ??-pinene, the repellency of lemon essential oil is possibly attributed to the presence of citral.     

Feeding deterrent activity of synthesized silver nanoparticles using Manilkara zapota leaf extract against the house fly, Musca domestica (Diptera: Muscidae)

With a greater awareness of the hazards associated with the use of synthetic organic insecticides, there has been an urgent need to explore suitable alternative products for pest control. Musca domestica is ubiquitous insect that has the potential to spread a variety of pathogens to humans and livestock. They are mechanical carriers of more than hundred human and animal intestinal diseases and are responsible for protozoan, bacterial, helminthic, and viral infections. The present work aimed to investigate the feeding deterrent activity of synthesized silver nanoparticles (Ag NPs) using leaf aqueous extract of Manilkara zapota against M. domestica. The synthesized Ag NPs were recorded from UV–vis spectrum at 421 nm and scanning electron microscopy confirm the biosynthesis and characterization of Ag NPs with spherical and oval in shape and size of 70–140 nm. The FTIR analysis of the purified nanoparticles showed the presence of bands 1,079, 1,383, 1,627, 2,353, and 2,648 cm^?1, which were complete synthesis of AgNPs; the XRD pattern of AgNPs showed diffraction peaks at 2θ values of 38.06°, 44.37°, 64.51°, and 77.31° sets of lattice planes were observed (111), (200), (220), and (311) facts of silver, respectively. Adult flies were exposed to different concentrations of the aqueous extract of synthesized Ag NPs, 1 mM silver nitrate (AgNO₃) solution and aqueous extract of M. zapota for 1, 2, and 3 h; however, AgNPs showed 72% mortality in 1 h, 89% mortality was found in 2 h, and 100% mortality was found in 3 h exposure at the concentration of 10 mg/mL and the leaf aqueous extract showed 32% mortality in 1 h, 48% mortality was found in 2 h, and 83% mortality was found in 3 h exposure at concentration of 50 mg/mL. The most efficient activity was observed in synthesized Ag NPs against M. domestica (LD₅₀?=?3.64 mg/mL; LD₉₀?=?7.74 mg/mL), the moderate activity reported in the aqueous extract of M. zapota (LD₅₀?=?28.35 mg/mL; LD₉₀?=?89.19 mg/mL) and nil activity were observed in AgNO₃ solution at 3 h exposure time at 10 mg/mL. Dimethyl 2, 2-dichlorovinyl phosphate (DDVP) was used as a positive control and showed the LD₅₀ value of 3.38 mL/L. These results suggest that the synthesized Ag NPs have the potential to be used as an ideal eco-friendly approach for the control of the adult of M. domestica. This method is considered as a new approach to control sanitary pest. Therefore, this study provides first report on the feeding deterrent activity of synthesized Ag NPs against housefly.     

Oxygen sensing and conducted vasomotor responses in mouse cremaster arterioles in situ

This study examines mechanisms by which changes in tissue oxygen tension elicit vasomotor responses and whether localized changes in oxygen tension initiates conducted vasomotor responses in mouse cremaster arterioles. Intravital microscopy was used to visualize the mouse cremaster microcirculation. The cremaster was superfused with Krebs’ solution with different oxygen tensions, and a gas exchange chamber was used to induce localized changes in oxygen tension. In arterioles where red blood cells were removed by buffer perfusion, arterioles responded with same magnitudes of vasodilatation (ΔD?=?16.0?±?4.9 μm) when changing from high (PO₂?=?242.5?±?13.3 mm Hg) to low (PO₂?=?22.5?±?4.8 mm Hg) oxygen tension as seen in the intact cremaster circulation (ΔD?=?18.7?±?1.0 μm). Blockade of NO synthases by L-NAME and adenosine receptors by DPCPX had no effects on vasomotor responses to low or high oxygen. Induction of localized low (PO₂?=?23.3?±?5.7 mmHg) or high (PO₂?=?300.0?±?25.7 mm Hg) oxygen tension caused vasodilatation or -constriction locally and at a site 1,000 μm upstream (distantly). Glibenclamide blocker of ATP-sensitive K⁺ channels inhibited vasodilatation and -constriction to low (PO₂?=?16.0?±?6.4 mm Hg) and high (PO₂?=?337.4?±?12.8 mm Hg) oxygen tension. 1) ATP-sensitive K⁺ channels seem to mediate, at least in part, vasodilatation and vasoconstriction to low and high oxygen tension; 2) Red blood cells are not necessary for inducing vasodilatation and vasoconstriction to low or high oxygen tension; 3) localized changes in the oxygen tension cause vasomotor responses, which are conducted upstream along arterioles in mouse cremaster microcirculation.     

Effects of lobeline, a nicotinic receptor ligand, on the cloned Kv1.5

The goal of the present study was to examine the effects of lobeline, an agonist at nicotinic receptors, on cloned Kv channels, Kv1.5, Kv3.1, Kv4.3, and human ether-a-gogo-related gene (HERG), which are stably expressed in Chinese hamster ovary (CHO) or human embryonic kidney 293 (HEK293) cells. Whole-cell patch-clamp experiments revealed that lobeline accelerated the decay rate of Kv1.5 inactivation, decreasing the current amplitude at the end of the pulse in a concentration-dependent manner with a half-maximal inhibitory concentration (IC₅₀) value of 15.1 μM. Using a time constant for the time course of drug-channel interaction, the apparent association (k ₊₁), and dissociation rate (k _?1) constants were 2.4 μΜ^?1?s^?1 and 40.9 s^?1, respectively. The calculated K _D was 17.0 μΜ. Lobeline slowed the decay rate of the tail current, resulting in a tail crossover phenomenon. The inhibition of Kv1.5 by lobeline steeply increased at potentials between ?10 and +10 mV, which corresponds to the voltage range of channel activation. At more depolarized potentials a weaker voltage dependence was observed (δ?=?0.26). The voltage dependence of the steady-state activation curve was not affected by lobeline, but lobeline shifted the steady-state inactivation curve of Kv1.5 in the hyperpolarizing direction. Lobeline produced use-dependent inhibition of Kv1.5 at frequencies of 1 and 2 Hz, and slowed the recovery from inactivation. Lobeline also inhibited Kv3.1, Kv4.3, and HERG in a concentration-dependent manner, with IC₅₀ values of 21.7, 28.2, and 0.34 μM, respectively. These results indicate that lobeline produces a concentration-, time-, voltage-, and use-dependent inhibition of Kv1.5, which can be interpreted as an open-channel block mechanism.     

Activity assessment of Tunisian olive leaf extracts against the trophozoite stage of Acanthamoeba

The olive tree (Olea europaea, Oleaceae) has historically provided huge economic and nutritional benefits to the Mediterranean basin. In fact, olive leaf extracts have also been used by native people of this area in folk medicine to treat fever and other diseases such as malaria. Recently, several studies have focused on the extraction of high-added-value compounds from olive leaves. However, no previous studies have been developed in order to evaluate the activity of these extracts against Acanthamoeba. In the present work, olive leaf extracts from five different Tunisian varieties of olive trees (Chemlali Tataouine, Zarrazi, Toffehi, Dhokkar, and Limouni) were obtained by using three different solvents, and their activity against the trophozoite stage of Acanthamoeba castellanii Neff was screened. The IC₅₀/96 h (50 % parasite growth inhibition) was chosen as the appropriate and comparable data to give as previously described. It could be observed that the amoebicidal activity was dose dependent. Trophozoite growth was inhibited by all the tested extracts with IC₅₀ ranging from 8.234?±?1.703 μg/ml for the alcoholic mixture of the Dhokkar extract to 33.661?±?1.398 μg/ml for the methanolic extract of the Toffehi variety. The activity in fact was affected especially by the tested variety and not by the solvent extraction, the Dhokkar variety being the most active one as mentioned above.     

Temperature dependence of habituation of the initial responses to cold-water immersion

The initial responses to cold-water immersion, evoked by stimulation of peripheral cold receptors, include tachycardia, a reflex inspiratory gasp and uncontrollable hyperventilation. When immersed naked, the maximum responses are initiated in water at 10°C, with smaller responses being observed following immersion in water at 15°C. Habituation of the initial responses can be achieved following repeated immersions, but the specificity of this response with regard to water temperature is not known. Thirteen healthy male volunteers were divided into a control (C) group (n?=?5) and a habituation (H) group (n?=?8). Each subject undertook two 3-min head-out immersions in water at 10°C wearing swimming trunks. These immersions took place at a corresponding time of day with 4 days separating the two immersions. In the intervening period the C group were not exposed to cold water, while the H group undertook another six, 3-min, head-out immersions in water at 15°C. Respiratory rate (f _R), inspiratory minute volume (V˙ _I) and heart rate (f _H) were measured continuously throughout each immersion. Following repeated immersions in water at 15°C, the f _R, V˙ _I and f _H responses of the H group over the first 30 s of immersion were reduced (P??1, 50.5?l?·?min^?1 and 114 beats?·?min^?1 respectively, to 19.8 breaths?·?min^?1, 26.4?l?·?min^?1 and 98 beats?·?min^?1, respectively. In water at 10°C these responses were reduced (P??1, 67.6?l?· min^?1 and 128 beats?·?min^?1 to 24.0 breaths?·?min^?1, 29.5?l?·?min^?1 and 109 beats?·?min^?1, respectively over a corresponding period of immersion. Similar reductions were observed during the last 2.5?min of immersions. The initial responses of the C group were unchanged. It is concluded that habituation of the cold shock response can be achieved by immersion in warmer water than that for which protection is required. This suggests that repeated submaximal stimulation of the cutaneous cold receptors is sufficient to attenuate the responses to more maximal stimulation.     

Insecticidal activity of essential oils from native medicinal plants of Central Argentina against the house fly, <Emphasis Type="Italic">Musca domestica</Emphasis> (L.)

The insecticidal activity of nine essential oils (EOs) against the house fly (Musca domestica) was evaluated by placing flies in a screw-cap glass jar holding a piece of EO-treated cotton yarn. The dose necessary to kill 50% of flies (LC₅₀) in 30 min was determined at 26?±?1°C. The EOs showed LC₅₀ values ranging from 0.5 to 46.9 mg/dm³. The EO from Minthostachys verticillata was the most potent insecticide (LC₅₀?=?0.5 mg/dm³) followed by EOs from Hedeoma multiflora (LC₅₀?=?1.3 mg/dm³) and Artemisia annua (LC₅₀?=?6.5 mg/dm³). The compositions of the nine EOs, obtained by hydrodistillation of medicinal herbs, were analyzed by gas chromatography/mass spectroscopy. These analyses showed that (4R)(+)-pulegone (69.70%), menthone (12.17%), and limonene (2.75%) were the principal components of M. verticillata EO. (4R)(+)-pulegone was also the main constituent (52.80%) of H. multiflora, while artemisia ketone (22.36%) and 1,8-cineole (16.67%) were the major constituents of A. annua EO. The terpene (4R)(+)-pulegone showed a lower toxicity (LC₅₀?=?1.7 mg/dm³) than M. verticillata or H. multiflora EOs. Dimethyl 2,2-dichlorovinyl phosphate, selected as a positive control, showed an LC₅₀ of 0.5 mg/dm³. EOs from M. verticillata and H. multiflora show promise as natural insecticides against houseflies.