Dermal absorption of chlorpyrifos (CPF), an organophosphate (OP) pesticide, is important because of its popular use. Stress has been reported to exacerbate neurotoxic effects of certain OP pesticides; however, quantitative studies to corroborate this are not reported. This study correlates the changes in acetylcholinesterase (AChE) levels and neuronal counts in areas of the hippocampus to consecutive exposure of stress, heat and CPF. Male mice (60 days) were segregated into six groups: one control, one stress control, and four treated groups (n=10). CPF was applied in doses of 1/2 and 1/5 of dermal LD50 (E1 and E2) over the tail of mice under occlusive bandages for 3 weeks. Stress control [(s) C] mice were subjected to swim stress at 38 degrees C (6 mins/day, 3 weeks). (s) E1 and (s) E2 were subjected to swim stress before CPF application. Blood and brain AChE levels were estimated using a spectrofluorometric method (Amplex Red). Pyramidal neurons of the cornu ammonis of the hippocampus under Nissl stain from histological sections were counted per unit area of section and analyzed statistically using one way ANOVA. Swim stress at 38 degrees C aggravated reduction of serum AChE by dermal exposure to CPF by 19.7%. Neurons of CA3 and CA1 regions of the hippocampus showed significant reduction in neuronal counts in (s) E1 and (s) E2 groups compared to E1 and E2 groups. Whereas application of CPF 1/2 dermal LD50 (E1) showed significant reduction of neuronal counts only in the CA3 area.
The impact of green-synthesised mosquitocidal nanoparticles on non-target aquatic predators is poorly studied. In this research, we proposed a single-step method to synthesise silver nanoparticles (Ag NP) using the seed extract of Melia azedarach. Ag NP were characterised using a variety of biophysical methods, including UV-vis spectrophotometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. In laboratory assays on Anopheles stephensi, Ag NP showed LC50 ranging from 2.897 (I instar larvae) to 14.548 ppm (pupae). In the field, the application of Ag NP (10 × LC50) lead to complete elimination of larval populations after 72 h. The application of Ag NP in the aquatic environment did not show negative adverse effects on predatory efficiency of the mosquito natural enemy Cyclops vernalis. Overall, this study highlights the concrete possibility to employ M. azedarach-synthesised Ag NP on young instars of malaria vectors.
Malaria remains a major public health problem due to the emergence and spread of Plasmodium falciparum strains resistant to chloroquine. There is an urgent need to investigate new and effective sources of antimalarial drugs. This research proposed a novel method of fern-mediated synthesis of silver nanoparticles (AgNP) using a cheap plant extract of Pteridium aquilinum, acting as a reducing and capping agent. AgNP were characterized by UV-vis spectrophotometry, Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). Phytochemical analysis of P. aquilinum leaf extract revealed the presence of phenols, alkaloids, tannins, flavonoids, proteins, carbohydrates, saponins, glycosides, steroids, and triterpenoids. LC/MS analysis identified at least 19 compounds, namely pterosin, hydroquinone, hydroxy-acetophenone, hydroxy-cinnamic acid, 5, 7-dihydroxy-4-methyl coumarin, trans-cinnamic acid, apiole, quercetin 3-glucoside, hydroxy-L-proline, hypaphorine, khellol glucoside, umbelliferose, violaxanthin, ergotamine tartrate, palmatine chloride, deacylgymnemic acid, methyl laurate, and palmitoyl acetate. In DPPH scavenging assays, the IC50 value of the P. aquilinum leaf extract was 10.04 μg/ml, while IC50 of BHT and rutin were 7.93 and 6.35 μg/ml. In mosquitocidal assays, LC50 of P. aquilinum leaf extract against Anopheles stephensi larvae and pupae were 220.44 ppm (larva I), 254.12 ppm (II), 302.32 ppm (III), 395.12 ppm (IV), and 502.20 ppm (pupa). LC50 of P. aquilinum-synthesized AgNP were 7.48 ppm (I), 10.68 ppm (II), 13.77 ppm (III), 18.45 ppm (IV), and 31.51 ppm (pupa). In the field, the application of P. aquilinum extract and AgNP (10 × LC50) led to 100 % larval reduction after 72 h. Both the P. aquilinum extract and AgNP reduced longevity and fecundity of An. stephensi adults. Smoke toxicity experiments conducted against An. stephensi adults showed that P. aquilinum leaf-, stem-, and root-based coils evoked mortality rates comparable to the permethrin-based positive control (57, 50, 41, and 49 %, respectively). Furthermore, the antiplasmodial activity of P. aquilinum leaf extract and green-synthesized AgNP was evaluated against CQ-resistant (CQ-r) and CQ-sensitive (CQ-s) strains of P. falciparum. IC50 of P. aquilinum were 62.04 μg/ml (CQ-s) and 71.16 μg/ml (CQ-r); P. aquilinum-synthesized AgNP achieved IC50 of 78.12 μg/ml (CQ-s) and 88.34 μg/ml (CQ-r). Overall, our results highlighted that fern-synthesized AgNP could be candidated as a new tool against chloroquine-resistant P. falciparum and different developmental instars of its primary vector An. stephensi. Further research on nanosynthesis routed by the LC/MS-identified constituents is ongoing.
Exposure to organophosphate insecticides such as fenitrothion (FNT) in agriculture and public health has been reported to affect sperm quality. Antioxidants may have a potential to reduce spermatotoxic effects induced by organophosphate. The present study was carried out to evaluate the effects of palm oil tocotrienol-rich fraction (TRF) in reducing the detrimental effects occurring in spermatozoa of FNT-treated rats. Adult male Sprague-Dawley rats were divided into four equal groups: a control group and groups of rats treated orally with palm oil TRF (200 mg/kg), FNT (20 mg/kg) and palm oil TRF (200 mg/kg) combined with FNT (20 mg/kg). The sperm characteristics, DNA damage, superoxide dismutase (SOD) activity, and levels of reduced glutathione (GSH), malondialdehyde (MDA), and protein carbonyl (PC) were evaluated. Supplementation with TRF attenuated the detrimental effects of FNT by significantly increasing the sperm counts, motility, and viability and decreased the abnormal sperm morphology. The SOD activity and GSH level were significantly increased, whereas the MDA and PC levels were significantly decreased in the TRF+FNT group compared with the rats receiving FNT alone. TRF significantly decreased the DNA damage in the sperm of FNT-treated rats. A significant correlation between abnormal sperm morphology and DNA damage was found in all groups. TRF showed the potential to reduce the detrimental effects occurring in spermatozoa of FNT-treated rats.
Resistance to the bacteria-derived insecticides spinosad (Conserve), abamectin (Vertimec), Bacillus thuringiensis var kurstaki (Btk) (Dipel), B thuringiensis var aizawai (Bta) (Xentari), B thuringiensis crystal endotoxins Cry1Ac and Cry1Ca, and to the synthetic insecticide fipronil was estimated in a freshly-collected field population (CH1 strain) of Plutella xylostella (L) from the Cameron Highlands, Malaysia. Laboratory bioassays at G1 indicated significant levels of resistance to spinosad, abamectin, Cry1Ac, Btk, Cry1Ca, fipronil and Bta when compared with a laboratory insecticide-susceptible population. Logit regression analysis of F1 reciprocal crosses indicated that resistance to spinosad in the CH1 population was inherited as a co-dominant trait. At the highest dose of spinosad tested, resistance was close to completely recessive, while at the lowest dose it was incompletely dominant. A direct test of monogenic inheritance based on a back-cross of F1 progeny with CH1 suggested that resistance to spinosad was controlled by a single locus.
Field bioefficacy of residual-sprayed deltamethrin against Aedes vectors was evaluated in an urban residential area in Kuala Lumpur. The trial area consisted of single storey wood-brick houses and a block of flat. The houses were treated with outdoor residual spraying while the flat was used as an untreated control. Initial pre-survey using ovitrap surveillance indicated high Aedes population in the area. Deltamethrin WG was sprayed at a dosage of 25mg/m2 using a compression sprayer. The effectiveness of deltamethrin was determined by wall bioassay and ovitrap surveillance. The residual activity of 25mg/m2 deltamethrin was still effective for 6 weeks after treatment, based on biweekly bioassay results. Bioassay also indicated that both Aedes aegypti and Aedes albopictus were more susceptible on the wooden surfaces than on brick. Aedes aegypti was more susceptible than Ae. albopictus against deltamethrin. Residual spraying of deltamethrin was not very effective against Aedes in this study since the Aedes population in the study area did not reduce as indicated by the total number of larvae collected using the ovitrap (Wilcoxon Sign Test, p> 0.05). Further studies are required to improve the effectiveness of residual spraying against Aedes vectors.
Currently, nano-formulated mosquito larvicides have been widely proposed to control young instars of malaria vector populations. However, the fate of nanoparticles in the aquatic environment is scarcely known, with special reference to the impact of nanoparticles on enzymatic activity of non-target aquatic invertebrates. In this study, we synthesized CdS nanoparticles using a green protocol relying on the cheap extract of Valoniopsis pachynema algae. CdS nanoparticles showed high toxicity on young instars of the malaria vectors Anopheles stephensi and A. sundaicus. The antimalarial activity of the nano-synthesized product against chloroquine-resistant (CQ-r) Plasmodium falciparum parasites was investigated. From a non-target perspective, we focused on the impact of this novel nano-pesticide on antioxidant enzymes acetylcholinesterase (AChE) and glutathione S-transferase (GST) activities of the mud crab Scylla serrata. The characterization of nanomaterials was carried out by UV-vis and FTIR spectroscopy, as well as SEM and XRD analyses. In mosquitocidal assays, LC50 of V. pachynema-synthesized CdS nanoparticles on A. stephensi ranged from 16.856 (larva I), to 30.301μg/ml (pupa), while for An. sundaicus they ranged from 13.584 to 22.496μg/ml. The antiplasmodial activity of V. pachynema extract and CdS nanoparticles was evaluated against CQ-r and CQ-sensitive (CQ-s) strains of Plasmodium falciparum. IC50 of V. pachynema extract was 58.1μg/ml (CQ-s) and 71.46μg/ml (CQ-r), while nano-CdS IC50 was 76.14μg/ml (CQ-s) and 89.21μg/ml (CQ-r). In enzymatic assays, S. serrata crabs were exposed to sub-lethal concentrations, i.e. 4, 6 and 8μg/ml of CdS nanoparticles, assessing changes in GST and AChE activity after 16days. We observed significantly higher activity of GST, if compared to the control, during the whole experiment period. In addition, a single treatment with CdS nanoparticles led to a significant decrease in AChE activity over time. The toxicity of CdS nanoparticles and Cd ions in aqueous solution was also assessed in mud crabs, showing higher toxicity of aqueous Cd ions if compared to nano-CdS. Overall, our results underlined the efficacy of green-synthesized CdS nanoparticles in malaria vector control, outlining also significant impacts on the enzymatic activity of non-target aquatic organisms, with special reference to mud crabs.
The bioefficacy of indoor residual-sprayed deltamethrin wettable granule (WG) formulation at 25 mg a.i./m2 and 20 mg a.i./m2 for the control of malaria was compared with the current dose of 20 mg/m2 deltamethrin wettable powder (WP) in aboriginal settlements in Kuala Lipis, Pahang, Malaysia. The malaria vector has been previously identified as Anopheles maculatus. The assessment period for the 20 mg/m2 dosage was six months, but for the 25 mg/m2 dosage, the period was 9 months. Collections of mosquitoes using the bare-leg techniques were carried out indoors and outdoors from 7:00 PM to 7:00 AM. All mosquitoes were dissected for sporozoites and parity. Larval collections were carried out at various locations to assess the extent and distribution of breeding of vectors. A high incidence of human feeds was detected during May 2005 and a low incidence during January 2005 for all the study areas. Our study showed that deltamethrin WG at 25 mg/m2 suppressed An. maculatus biting activity. More An. maculatus were caught in outdoor landing catches than indoor landing catches for all the study areas. The results indicate that 25 mg/m2 WG is good for controlling malaria for up to 9 months. Where residual spraying is envisaged, the usual two spraying cycles per year with 20 mg/m2 deltamethrin may be replaced with 25 mg/m2 deltamethrin WG every 9 months.
Diazinon (O,O-diethyl-O-[2-isopropyl-6-methyl-4-pyrimidinyl] phosphoro thioate), an organo-phosphate insecticide, has been used worldwide in agriculture and domestic for several years, which has led to a variety of negative effects in non target species including humans. However, its nephrotoxic effects and mechanism of action has not been fully elucidated so far. Therefore, the present study was aimed at evaluating the nephrotoxic effects of diazinon and its mechanism of action with special reference to its possible ROS generating potential in rats. Treatment of rats with diazinon significantly enhances renal lipid peroxidation which is accompanied by a decrease in the activities of renal antioxidant enzymes (e.g. catalase, glutathione peroxidise, glutathione reductase, glucose-6-phosphate dehydrogenase, glutathione S-transferase) and depletion in the level of glutathione reduced. In contrast, the activities of renal γ-glutamyl transpeptidase and quinone reductase were increased. Parallel to these changes, diazinon treatment enhances renal damage as evidenced by sharp increase in blood urea nitrogen and serum creatinine. Additionally, the impairment of renal function corresponds histopathologically. In summary, our results indicate that diazinon treatment eventuates in decreased renal glutathione reduced, a fall in the activities of antioxidant enzymes including the enzymes involved in glutathione metabolism and excessive production of oxidants with concomitant renal damage, all of which are involved in the cascade of events leading to diazinon-mediated renal oxidative stress and toxicity. We concluded that in diazinon exposure, depletion of antioxidant enzymes is accompanied by induction of oxidative stress that might be beneficial in monitoring diazinon toxicity.
The objective of this study was to study the possible reproductive adverse effects of the diazinon on rat offspring exposed in utero and during lactation. Dams were gavaged daily (10, 15, and 30 mg/kg) before mating, during mating, and during pregnancy and lactation in separate groups. Reproductive outcome data of dams were examined. Body weight, testis weight, testicular marker enzyme activities (alkaline phosphatase, acid phosphatase, lactate dehydrogenase, and glucose-6-phosphate dehydrogenase), qualitative and quantitative testicular and epididymal histology, and immunohistochemisty for 3-β-hydroxysteroid dehydrogenase (HSD) were examined in male offspring at puberty and adulthood. The 30-mg/kg dose induced significant adverse effects at both puberty and adulthood in offspring. At puberty the male offspring showed a decrease in testicular weight, degenerative changes, and 3-β-HSD. Moreover, an increase in activity of alkaline and acid phosphatase also was observed. At adulthood, there was a decrease in testicular weight and 3-β-HSD with an increase in the levels of testicular marker enzyme. There was evidence of some adverse reproductive effects in male offspring at the 15-mg/kg dose. Most of the adverse effects were irreversible and were evident at both puberty and adulthood in offspring, although a few parameters reverted back to the normal growth pattern. Hence, diazinon is a reproductive toxicant in male offspring, which caused significant damage to the testes when exposed during prenatal and postnatal life.