Study on embryonic effects of neonicotinoid insecticide on chick embryos

IntroductionNeonicotinoids are a group of insecticides derived from nicotine isolated from the tobacco plant. Imidacloprid is a widely applied pesticide due to their higher affinity for insect nicotinic acetylcholine receptors. Like nicotine, it acts on nervous system. Worldwide, it is considered to be one of the insecticides used in the largest volume. It has a wide diversity of uses in agriculture, on turf, on pets, and for household pests.MethodsPresent study was carried out in the Department of Anatomy Government Medical College, Ambedkar Nagar and Santosh Medical College Ghaziabad U.P. on 280 fertile eggs of white leghorn chicken obtained from government poultry farm after taking permission from animal ethical committee. Chicken eggs after having been exposed to Imidacloprid with doses of 5 μg, 12.5 μg, 25 μg, and 50 μg in a volume of 5 μl, 12.5 μl, 25 μl and 50 μl respectively and control same as test group. The embryos were terminated on 18th and 20th days, egg shell broken with a scalpel and embryos removed. Gross abnormalities observed and recorded in all embryos.ResultsThe results show that experimental group had comparatively more cases of delayed and growth retardation resulting into failure of retraction of yolk sac, limbs defects, neural tube defects as compared to controls. Comparatively higher doses proved more toxic and also caused many developmental defects.DiscussionNeonicotinoid exposure increases the risks of developmental defects with increasing embryonic age. Imidacloprid caused developmental delays and defects on nervous system.     

Celery-based topical repellents as a potential natural alternative for personal protection against mosquitoes

Celery-based products were investigated for chemical composition, skin irritation, and mosquito repellency in comparison to commercial repellents and the standard chemical, N,N-diethyl-3-methylbenzamide (DEET), with a goal to develop a natural alternative to synthetic repellents for protection against mosquitoes. Chemical identification by gas chromatography coupled with mass spectrometry discovered that the major constituents of Apium graveolens hexane extract (AHE) were 3-n-butyl-tetrahydrophthalide (92.48%), followed by 5.10% β-selinene and 0.68% γ-selinene. Evaluation of skin irritation in 27 human volunteers revealed no irritant potential from 25% ethanolic AHE solution. Laboratory investigated repellent against female Aedes aegypti mosquitoes demonstrated that G10 formula, the best AHE-developed product, provided remarkable repellency with a median protection time of 4.5 h (4.5–5 h), which was greater than that of ethanolic DEET solution (25% DEET, 3.5 h) and comparable to that of the best commercial repellent, Insect Block 28 (28.5% DEET, 4.5 h). According to significantly promising results, including highly effective repellency and no potential skin irritation or other side effects, the G10 formula is a worthwhile product that has the promise of being developed for commercialized registration. This developed AHE product could be an acceptable and affordable alternative to conventional synthetic chemicals in preventing mosquito bites, and in turn, helping to interrupt mosquito-borne disease transmission.     

Energetic cost of insecticide resistance in Culex pipiens mosquitoes

The extensive use of insecticides to control vector populations has lead to the widespread development of different mechanisms of insecticide resistance. Mutations that confer insecticide resistance are often associated to fitness costs that prevent them from spreading to fixation. In vectors, such fitness costs include reductions in preimaginal survival, adult size, longevity, and fecundity. The most commonly invoked explanation for the nature of such pleiotropic effects of insecticide resistance is the existence of resource-based trade-offs. According to this hypothesis, insecticide resistance would deplete the energetic stores of vectors, reducing the energy available for other biological functions and generating trade-offs between insecticide resistance and key life history traits. Here we test this hypothesis by quantifying the energetic resources (lipids, glycogen, and glucose) of larvae and adult females of the mosquito Culex pipiens L. resistant to insecticides through two different mechanisms: esterase overproduction and acetylcholinesterase modification. We find that, as expected from trade-off theory, insecticide resistant mosquitoes through the overproduction of esterases contain on average 30% less energetic reserves than their susceptible counterparts. Acetylcholinesterase-modified mosquitoes, however, also showed a significant reduction in energetic resources (20% less). We suggest that, in acetylcholinesterase-modified mosquitoes, resource depletion may not be the result of resource-based trade-offs but a consequence of the hyperactivation of the nervous system. We argue that these results not only provide a mechanistic explanation for the negative pleiotropic effects of insecticide resistance on mosquito life history traits but also can have a direct effect on the development of parasites that depend on the vector's energetic reserves to fulfil their own metabolic needs.     

Silica nanoparticle: a potential new insecticide for mosquito vector control

Presently, there is a need for increased efforts to develop newer and effective methods to control mosquito vectors as the existing chemical and biological methods are not as effective as in earlier period owing to different technical and operational reasons. The use of nanomaterial products in various sectors of science including health increased during the last decade. We tested three types of nanosilica, namely lipophilic, hydrophilic and hydrophobic, to assess their larvicidal, pupicidal and growth inhibitor properties and also their influence on oviposition behaviour (attraction/deterrence) of mosquito species that transmit human diseases, namely malaria (Anopheles), yellow fever, chickungunya and dengue (Aedes), lymphatic filariasis and encephalitis (Culex and Aedes). Application of hydrophobic nanosilica at 112.5?ppm was found effective against mosquito species tested. The larvicidal effect of hydrophobic nanosilica on mosquito species tested was in the order of Anopheles stephensi?>?Aedes aegypti?>?Culex quinquefasciatus, and the pupicidal effect was in the order of A. stephensi?>?C. quinquefasciatus?>?Ae. aegypti. Results of combined treatment of hydrophobic nanosilica with temephos in larvicidal test indicated independent toxic action without any additive effect. This is probably the first report that demonstrated that nanoparticles particularly nanosilica could be used in mosquito vector control.     

Deltamethrin, a pyrethroid insecticide, could be a potential antidepressant agent

Antidepressants, including tricyclic antidepressants, monoamine oxidase inhibitors, selective serotonin reuptake inhibitors and serotonin-noradrenalin reuptake inhibitors, are the main biological treatment for major depression. However, not all depressed patients improve clinically despite appropriate treatment. Thus, the exploration of novel antidepressants with novel mechanisms of action may help to develop more effective agents. Deltamethrin is a pyrethroid insecticide that is a widely used and has a low acute toxicity in mammals. Recent studies in vivo and in vitro have shown that the inducible effect of deltamethrin on brain-derived neurotrophic factor (BDNF) gene expression is very potent and tends to be sustained. With recent evidence that the activation of the BDNF-dependent pathway plays an important role in the mechanism of antidepressant therapeutic action, deltamethrin or derivatives thereof could have potential antidepressant therapeutic effects. Further evaluation of the therapeutic and toxic effects of this drug in animal models is needed before clinical trials can begin.     

Imiquimod: a potential weapon against Dupuytren contracture

Dupuytren disease is a proliferative fibroplasia of the subcutaneous palmar tissue, occurring in the form of nodular and cords. Evidence is certainly accumulating for raised levels in Dupuytren's tissue of growth factors known to stimulate fibroblasts, Interleukin-1, basic fibroblast growth factor, transforming growth factor-beta, prostaglandin-F2, prostaglandin-E2, platelet derived growth factor and connective tissue growth factor have been suggested to have a role. Immune modification of profibrotic cytokines would provide a novel means to treat dupuytren contracture. Imiquimod cream 5% (Aldara) is an immune modifier, that downregulates transforming growth factor-beta and fibroblast growth factor-2 (the two most important cytokine in producing fibrosis). Based on previous mentioned evidence we suggest: imquimod as a potential drug for dupuytren contracture treatment.     

A cyanobacterial mutant resistant against a bleaching herbicide

The nitrogen fixing cyanobacterium Nostoc muscorum has been found to be sensitive to the herbicide SAN 6706 [4-chloro-5 (dimethylamino)-2-(a,a,a,-trifluoro-m-tolyl)-3-(2H) pyridazinon] at 30-45 microM within 15 min. The toxicity was more severe in combined nitrogen-free (Ncomb-free) medium than in a combined nitrogen medium; this enhancement was reversible by supplementation of the medium with 3 mM glucose or 5 microM ATP, serving as carbon and/or energy source in this organism. A mutant of this cyanobacterium resistant to 3 mM SAN 6706 has been isolated and characterized to perform nitrogenase activity in exogenous ATP supplemented Ncomb-free medium. However, it exhibited a moderate growth in combined nitrogen media in the absence of external ATP. The resistance factor is higher than 100. Simultaneously, this strain possesses a cross-resistance to methylamine, a well-known inhibitor of photophosphorylation, irrespective of the exogenous ATP supply. The behavior of the mutant suggests a defective phosphorylation in its photosynthetic system.     

Antimicrobial peptides: a potential arsenal against HIV infection

HIV (human immunodeficiency virus) infection is today a very important health issue worldwide, which demands new ways and strategies for its prevention and treatment. Several studies on the innate immunity against HIV infection have shown that antimicrobial peptides are associated with increased resistance to infection. In the present review, we briefly summarize the major characteristics of antimicrobial peptides from human and several species of plants, amphibians, insects and other animal species that have significant potential to be used as therapeutic or prophylactic agents. The mechanisms of infection inhibition and viral replication blockade are also described in the context of the biology of infection.     

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.     

杭州尖音库蚊复组蚊虫对杀虫剂的抗性和酯酶同工酶的研究

用生物测定和淀粉电泳技术对采自杭州市西湖区的尖音库蚊复组蚊虫的抗性水平及与抗性有关的酯酶进行了研究.结果表明西湖区种群对DDVP、三氯杀虫酯、残杀威、溴氰菊酯、氯菊酯的抗性分别是上海敏感品系的5.35、1.69、4.73、4.8、2.65倍.在1997～19993年间,对5种杀虫药剂的抗性分析,其中对氯菊酯的抗性逐年增高,1999年的LC50比1997年增高14.5%;而对溴氰菊酯的抗性则呈降低趋势,1998和1999年的抗性无变化,其LC50比1997年降低了36%;对残杀威的抗性1998和1999年比1997年均有提高,抗性水平分别增高了38%和36.2%;对DDVP和三氯杀虫酯的抗性则无明显变化.酯酶分析结果显示,该种群存在过量产生的非特异性酯酶Estβ11和Estα2/β2,存在着较大的中性多态性,在有机磷的选择下,这些中性多态性可能会成为基因扩增的潜在因素.     

Antitumour antibiotics with potent activity against multidrug resistant (MDR) Staphylococcus aureus: a new approach to targeting resistant bacteria

As hospital reports of strains of resistant bacteria are continuing to increase, a new approach is required for the identification of small molecules with antibacterial activity. Natural products that bind covalently to their biological target have been largely unexplored, although in the field of cancer chemotherapy, such molecules have been shown to counter resistance developed through efflux mechanisms. The azinomycins are potent antitumour agents that alkylate DNA and one of the natural products, compound 1, is a mono-alkylator that has been reported to retain potent antitumour activity. All four diastereomers of 1 were synthesized via a route involving late stage introduction of the epoxide stereocentre and separation of the resulting compounds. A non-alkylating analogue and a potential alkylator that cannot intercalate were also made. All four diastereomers are potent antibacterial agents in cell lines containing efflux-based resistance mechanisms. MIC values in the range of 0.25-1.0 microg/ml were observed. Comparison with the antitumour activity of the compounds suggests that the antibacterial activity stems from a similar mechanism of action involving DNA alkylation. As the ultimate molecular target of the azinomycins is unknown, bacterial strains may represent an interesting route for the discovery of the downstream mechanisms affected by DNA alkylation.     

Insecticidal and larvicidal activities of medicinal plant extracts against mosquitoes

In recent years, use of environment friendly and biodegradable natural insecticides of plant origin have received renewed attention as agents for vector control because they are rich in bioactive chemicals, active against a limited number of species including specific target insects, and biodegradable. The present study was carried out to evaluate the adulticidal, repellent, and larvicidal activity of crude hexane, ethyl acetate, and methanol extracts of eight plants, viz. Aristolochia indica L., Cassia angustifolia Vahl, Diospyros melanoxylon Roxb., Dolichos biflorus L., Gymnema sylvestre (Retz) Schult, Justicia procumbens L., Mimosa pudica L., and Zingiber zerumbet L., were tested against adult and early fourth instar larvae of Culex gelidus Theobald and Culex quinquefasciatus Say (Diptera: Culicidae). The effective adult mortality was observed in methanol extract of A. indica, ethyl acetate extract of D. biflorus, and ethyl acetate and hexane extract of Z. zerumbet against C. gelidus and C. quinquefasciatus (LD₅₀ = 37.75, 78.56, 129.44, 86.13, 80.06, 112.42, 53.83, and 46.61; LD₉₀ = 166.83, 379.14, 521.50, 289.83, 328.18, 455.72, 181.15, and 354.50 ppm, respectively). Complete protections for 150 min were found in hexane and methanol extract of A. indica and Z. zerumbet at 1,000 ppm against mosquito bites. The highest larval mortality was found in the hexane extract of Z. zerumbet, ethyl acetate extract of D. biflorus, and methanol extracts of A. indica against C. gelidus (LC₅₀ = 26.48, 33.02, and 12.47 ppm; LC₉₀ = 127.73, 128.79, and 62.33 ppm) and against C. quinquefasciatus (LC₅₀ = 69.18, 34.76, and 25.60 ppm; LC₉₀ = 324.40, 172.78, and 105.52 ppm), respectively, after 24 h. The plant extracts are potential to be used as an ideal eco-friendly approach for the control of the Japanese encephalitis vector, C. gelidus, and lymphatic filariasis vector, C. quinquefasciatus.