•Low cost production of silver nanoparticles using Azadirachta indica (Common Indian neem) leaf extract.•Single step production of silver nanoparticles.•Silver nanoparticles have potential ...antimicrobial properties.
Rapid synthesis of silver nanoparticles through economically feasible green chemistry approach is highly desirable. In this study we have developed a method to synthesize silver nanoparticles by mixing silver solution with leaf extract of Azadirachta indica without using any surfactant or external energy. In this method, physiologically stable, bio-compatible Ag nanoparticles were formed. These functionalized AgNPs could be used for targeted drug delivery with enhanced therapeutic efficacy and minimal side effects. Extracellular synthesis of metal nanoparticles using extracts of plants like A. indica (Neem), and Zingiber officinale (Ginger) has been successfully carried out. In this article AgNPs formation using Azadirachta indica has been thoroughly discussed. It is well known that on treating the metallic salt solution with some plant extracts, a rapid reduction occur leading to the formation of highly stable metal nanoparticles. With this method rapid synthesis of nanoparticles was observed to occur; i.e. reaction time was 1–2h as compared to 2–4days required by microorganisms. These nanoparticles were analyzed by various characterization techniques to reveal their morphology, chemical composition, and antimicrobial activity. TEM image of these NPs indicated the formation of spherical, non-uniform, poly dispersed nanoparticles. A detailed study of anti-microbial activity of nanoparticles was carried out.
Aedes aegypti (L.) is known as vector of dengue and chikungunya fever. Larvicides are used to control this vector. We evaluated the efficacy of newly developed formulations of larvicides to control ...Ae. aegypti under field conditions for 24 weeks post single application. Mosdop P and Mosdop TB containing diflubenzuron (2% and 40 mg/tablet, respectively) as the active ingredient, were applied at a dosage of 0.1 mg a.i./1 and Mosquit TB10, Mosquit TB100 and Temecal containing temephos (1%, 10% and 1%, respectively) as the active ingredient were applied at a dosage of 1 mg active ingredent (a.i.) to 200 liter water storage jars. Two water regimens were used in the jars: in one regimen the jar was kept full of water all the time and in the other regimen a full jar had half the volume removed and refilled weekly. The larvicidal efficacy was reported as the level of inhibition of emergence (IE%) calculated based on the pupal skins in the jars versus the original number of larvae added. Mosdop P, Mosdop TB, Mosquit TB10, Mosquit TB100 and Temecal showed complete larvicidal efficacy (100% IE) in the constantly full jars for 16, 17, 14, 20 and 13 weeks posttreatment, respectively; in the jars where half the volum of water was replaced weekly, the larvicides had complete larvicidal efficacy (100% IE) for 19, 20, 17, 24 and 15 weeks post-treatment, respectively. The five larvicide regimens evaluated in this study are effective for controlling Ae. aegypti larvae.
Culiseta incidens Thomson is distributed over most of the western USA and Canada northward to Alaska. Because this mosquito is difficult to colonize, its biology has not been well investigated. We ...colonized this species in 1998 and studied the effects of temperature on various aspects of its life cycle. The time required for egg melanization and the duration of the egg stage were negatively correlated with temperature. The proportion of fertile egg rafts was temperature-independent. An inverse relationship existed between temperature and egg hatch. Molting and stadium duration after hatching were temperature-dependent, with higher temperature accelerating development and molting. Larvae and pupae experienced lower mortality and higher molting success at lower temperatures. Survivorship of adult mosquitoes fed on sugar solution was inversely proportional to temperature, lethal times for 50% mortality (LT50) were greater at the lower temperature than at the higher temperature. Females survived longer than did males at all test temperatures. Because this species is eurygamous, mating only occurred in large cages. Mating success was also affected by temperature. At the test temperatures, 20 degrees C, 25 degrees C and 30 degrees C, mating started from 3-5 days after emergence and reached a peak on days 13-15 after emergence. Maximum mating rates at 20 degrees C and 25 degrees C were higher than at 30 degrees C. Blood feeding, as indicated by cumulative feeding rates, was affected by cage size, mosquito age and temperature. Mosquitoes in large cages exhibited a much higher feeding rate than in small cages. With age, the cumulative blood feeding rate increased, with the highest rate at 25 degrees C, followed by 20 degrees C and 30 degrees C. At all temperatures tested, most of the blood fed females were mated.
Diethyl methyl benzamide, or deet, a commercial plant-based repellent (Repel Care), and essential ils from 3 species of plants (finger root rhizomes, guava leaves, and turmeric rhizomes), steam ...distillated and formulated as insect repellents, were evaluated in the field on human volunteers against hematophagous mosquitoes, black flies, and land leeches in Thailand. Field trials were conducted against wild mosquitoes in Bang Bua Thong District, Nonthaburi Province, and in the Thap Lan National Park Headquarters, Nadee District, Pranchinburi Province; anthroophilic black flies (Diptera: Simuliidae) at the Forestry Fire Control Station in Doi Inthanon National Park, Chomthong district, Chiang Mai Province; and land leeches (Arhynchobdellida: Haemadipsidae) in the Khao Yai National Park, Pak Chong District, Nakhon Ratchasima Province. The 3 experimental plant-based essential oil formulations as well as Repel Care and deet provided complete protection from mosquito landing and biting for up to 9 h (duration of the experiment). Similar results were obtained with the 5 products against black flies, providing 100% protection for 9 h but 96-82% protection after 10 and 11 h posttreatment. The 5 repellent products also provided 100% protection against land leeches for at least 8 h. Thi is the 1st report of repellency of plant-based repellents against black flies and land leeches in Thailand. The identification and availability of inexpensive sources of plant-based oils, i.e., finger root rhizomes, guava leaves, and turmeric rhizomes providing long-lasting repellency against blood-sucking organisms are promising leads into commercial production of relatively safe and effective repellents.
In order to develop and utilize new botanical insecticides originating from neem (Azadirachta indica A. Juss) in mosquito control programs as a potential larvicide, the antifeedant activity of three ...formulations of neem against the larvae of Culex tarsalis Coquillett and Culex quinquefasciatus Say was investigated under laboratory conditions. A significant antifeedancy was indicated at 5 ppm and 10 ppm azadirachtin (AZ) for all formulations and both species. Within the test concentration range of AZ (1-10 ppm), 5 ppm was the minimum effective concentration for antifeedancy in most cases. Some differences in larval susceptibility in terms of antifeedancy to the test formulations were noted between the two species. The Cx. tarsalis larvae were more susceptible than Cx. quinquefasciatus larvae to Azad EC 4.5 at 1 ppm during the first 15-min exposure period and at 5 and 10 ppm during the whole test period. The Cx. quinquefasciatus larvae were more susceptible than Cx. tarsalis larvae to Azatin WP 4.5 at 1, 5, and 10 ppm during the first 15-min exposure period or to Neemix EC 4.5 at 1 ppm during the first 45-min exposure period. The formulation-related differences in antifeedant activity appeared when the concentration increased from 1 to 10 ppm. In Cx. tarsalis, the Azad EC 4.5 and Neemix EC 4.5 were more effective than Azatin WP 4.5 at 5 ppm during the first 15-min exposure period and at 10 ppm during the whole test period. In Cx. quinquefasciatus, the Azatin WP 4.5 and Neemix EC 4.5 were more effective than Azad EC 4.5 at 1 ppm during the first 30-min exposure period, and at 5 ppm during the first 60-min exposure period, and at 10 ppm during the whole test period.
Purpose To present multiple imputation (MI) as an appropriate method to address missing values for a laboratory parameter (serum albumin) in an epidemiologic study. Methods A data set of patients who ...were hospitalized for invasive group A streptococcal infections was accessed. Age was the exposure of interest. The outcome was hospital mortality. Several variables, including serum albumin, were considered to be potential confounders. Of the 201 records, 91 had missing values for serum albumin. The MI procedure in SAS was used to perform 20 imputations of serum albumin by using a Markov chain Monte Carlo approach. Logistic regression was then performed on each of the 20 filled-in data sets, and the results were appropriately combined by using the MIANALYZE procedure. Results Age (≥55 years vs. 0–54 years) was not a risk factor for hospital mortality in the complete-case analysis ( n =110): adjusted odds ratio (OR)=2.43 (95% confidence interval CI: 0.79–7.53). Age was a significant risk factor in the imputed data set ( n =201): adjusted OR=3.08 (95% CI: 1.22–7.78). Conclusions Epidemiologists frequently encounter data sets that contain missing values. Traditional missing data techniques such as the complete-subject analysis may lead to biased results. We have demonstrated the use of a novel technique, MI, to account for missing data.
Laboratory and field-collected strains of Culex quinquefasciatus that were selected with Bacillus sphaericus strain 2362 in the laboratory for about 100 generations and attained 37- and 31-fold ...resistance, respectively, did not show marked cross-resistance to Bacillus thuringiensis spp. israelensis; only 2-3-fold tolerance was noted. However, they showed significant levels of cross-resistance to strains 1593 (6-22-fold) and 2297 (4-12-fold) of B. sphaericus. Possible mechanisms and management implications are discussed.
AIMS: Isolation and identification of bacteria capable of degrading organophosphate pesticide quinalphos and elucidation of its biodegradative pathway. METHODS AND RESULTS: A bacterium capable of ...degrading organophosphate pesticides was isolated from the pesticide‐contaminated soil samples by selective enrichment on quinalphos (QP) as a sole source of carbon and energy. The bacterial strain was identified as Ochrobactrum sp. strain HZM on the basis of its morphological and biochemical characteristics and by phylogenetic analysis based on 16S rRNA gene sequences. The organism utilized various organophosphate pesticides such as quinalphos, profenofos, parathion‐methyl and chlorpyrifos as growth substrates. Response surface methodology (RSM) showed optimum conditions for quinalphos degradation at pH 7 and 27°C. 2‐Hydroxyquinoxaline and diethyl phosphate were identified as metabolites of quinalphos degradation by HPLC and GC‐MS analysis. Cell‐free extract of Ochrobactrum sp. strain HZM grown on quinalphos contained the quinalphos hydrolase activity. CONCLUSIONS: A bacterial strain capable of degrading quinalphos was isolated and identified as Ochrobactrum sp. strain HZM. The organism utilized organophosphate pesticides quinalphos, profenofos, parathion‐methyl and chlorpyrifos as carbon sources. The organism degraded quinalphos by hydrolysis to yield 2‐hydroxyquinoxaline and diethyl phosphate which were further utilized as carbon sources. SIGNIFICANCE AND IMPACT OF THE STUDY: The isolated bacterium Ochrobactrum sp. strain HZM was versatile in degrading various organophosphate pesticides. There was complete mineralization of quinalphos by Ochrobactrum sp. This strain could potentially be useful in the bioremediation of soil and water contaminated with toxic organophosphate pesticides.
Two microbial mosquito larvicides, Bacillus thuringiensis ssp. israelensis (Bti) and Bacillus sphaericus (Bsph), have been shown to be highly effective in controlling mosquito larvae and have been ...used in larvicidal programs for many years. In exploring other modes of action of these agents, we studied the ovipositional response of Bsph susceptible and resistant Culex quinquefasciatus to aqueous suspensions of Bti and Bsph water dispersible granules (WDG). We quantified the level of mortality of adult mosquitoes caused by exposure to Bti and Bsph suspensions during oviposition. Significantly lower numbers of egg rafts were laid and collected from the treatments than the control regimen. There was an inverse relationship between Bacillus product concentrations and oviposition. As the concentration of Bti or Bsph increased from 0.0 to 2.0 mg/L, treated waters received progressively fewer egg rafts. In addition to the negative effects of Bacillus on oviposition, both male and female adult mosquitoes suffered high mortality on landing and imbibing on Bti and Bsph suspensions, the extent of mortality directly proportional to concentration. These two microbial agents used solely as mosquito larvicides thus have the additional benefits of reducing mosquito oviposition and killing adult mosquitoes, especially gravid females that come in contact with the treated water either for oviposition or drinking. Reducing the number of gravid females may also result in reduced transmission rates of pathogens. The combined effects of reduced oviposition and adult mortality could result in higher control potential of these microbial agents.
A substantial number of patients with early-stage colorectal cancer relapse from metastatic disease. Identification of these patients by genetic profiling of their primary tumours may allow more ...informed follow-up and tailored administration of adjuvant therapy. Primary tumours from 70 patients with early-stage and largely microsatellite-stable colorectal cancer were profiled using metaphase-based comparative genomic hybridization (CGH) and the aberrations confirmed independently in a subset of patients using microarray-based CGH. Of the 70 cancers, 61 were amenable to CGH, and follow-up data was available from 56 patients. Genomic aberrations were correlated with patients' survival using univariate, multivariate and Kaplan–Meier survival curves. Metastatic primary tumours exhibited more complex genomic aberrations than non-metastatic primary tumours. Loss of chromosome 4p was an independent prognostic factor in early-stage colorectal cancer using multivariate analysis (Hazard ratio, 9.6; 95% CI, 3.3–28; P=0.0001). Loss of both chromosome arms 8p and 18q had a statistically significant negative effect on disease-free survival. Moreover, primary tumours with loss of both chromosomes 4 and 14q bestowed poorer prognosis than tumours with loss of any one of the two chromosomes (P<0.0001). Genetic profiling of primary tumours of patients with early-stage colorectal cancer is of significant value in identifying the subset of patients who may relapse with metastatic disease. Accordingly, the molecular genetic features of primary tumours should be considered in the mainstream management of patients with this specific stage of the disease.
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