Beta Esterase Research Articles

Activity of insecticide detoxification enzymes in Pectinophora gossypiella (Saunders): Implications for insect pest management in cotton crops

The pink bollworm Pectinophora gossypiella is one of the most important endocarpic pests in cotton. In the management of this pest, the intensive use of synthetic insecticides has led to the reduction of its sensitivity to certain active ingredients. It is in this perspective that the study was conducted to determine the enzymes involved in the metabolism of insecticides in P. gossypiella. Insects were collected in five localities (Bouaké, Bouaflé, Vavoua, Sésuéla and Kounahiri) with high pest pressure in the southern cotton zone. The collected insects were ground for the determination of enzymes involved in insecticide metabolism. The analyses showed a significant increase in glutathione-δ-transferase activity in populations of Bouaké compared to the other localities. However, individuals from Séguéla expressed more esterase (alpha and beta) and oxidase activities. Alpha and beta esterase activities were also more expressed in Bouaflé individuals. The high enzymatic activity of esterases and oxidases in individuals from Séguéla and Bouaflé reflects a low sensitivity to insecticides in which esterases and oxidases are involved in the metabolism. On the other hand, in Bouaké, only glutathione- δtransferases are involved in the detoxification of insecticides.

Ace-1 Target Site Status and Metabolic Detoxification Associated with Bendiocarb Resistance in the Field Populations of Main Malaria Vector, Anopheles stephensi in Iran.

Anopheles stephensi is the main vector of malaria in Iran. This study aimed to determine the susceptibility of An. stephensi from the south of Iran to bendiocarb and to investigate biochemical and molecular resistance mechanisms in this species. Wild An. stephensi were collected from Hormozgan Province and reared to the adult stage. The susceptibility test was conducted according to the WHO protocols using bendiocarb impregnated papers supplied by WHO. Also, field An. Stephensi specimens were collected from south of Kerman and Sistan and Baluchistan Provinces. To determine the G119S mutation in the acetylcholinesterase (Ace1) gene, PCR-RFLP using AluI restriction enzyme and PCR direct-sequencing were performed for the three field populations and compared with the available GenBank data. Also, biochemical assays were performed to measure alpha and beta esterases, insensitive acetylcholinesterase, and oxidases in the strains. The bioassay tests showed that the An. stephensi field strain was resistant to bendiocarb (mortality rate 89%). Ace1 gene analysis revealed no G119S in the three field populations. Blast search of sequences revealed 98-99% identity with the Ace1 gene from Pakistan and India respectively. Also, the results of biochemical tests revealed the high activity of non-sensitive acetylcholinesterase, alpha and beta-esterase in the resistant strain compared to the susceptible strain. No G119S was detected in this study additionally the enhanced enzyme activity of esterases and acetylcholinesterase suggesting that resistance was metabolic. The use of alternative malaria control methods and the implementation of resistance management strategies are suggested in the study area.

Metabolite profiling and in-silico studies show multiple effects of insecticidal actinobacterium on Spodoptera littoralis

The polyphagous pest, Spodoptera littoralis (Boisduval), poses a significant global economic threat by gregariously feeding on over a hundred plant species, causing substantial agricultural losses. Addressing this challenge requires ongoing research to identify environmentally safe control agents. This study aimed to elucidate the insecticidal activity of the metabolite (ES2) from a promising endophytic actinobacterium strain, Streptomyces sp. ES2 EMCC2291. We assessed the activity of ES2 against the eggs and fourth-instar larvae of S. littoralis through spectrophotometric measurements of total soluble protein, α- and β-esterases, polyphenol oxidase (PPO), and catalase enzyme (CAT). The assessments were compared to commercial Biosad® 22.8% SC. Untargeted metabolomics using LC-QTOF-MS/MS identified 83 metabolic compounds as chemical constituents of ES2. The median lethal concentration (LC50) of ES2 (165 mg/mL) for treated Spodoptera littoralis eggs showed significant differences in polyphenol oxidase and catalase enzymatic activities, while the LC50 of ES2 (695 mg/mL) for treated S. littoralis fourth instar larvae showed lower significance in α- and β-esterase activities. Molecular docking of ES2 identified seven potent biocidal compounds, showing strong affinity to PPO and catalase CAT proteins in S. littoralis eggs while displaying limited binding to alpha and beta esterase proteins in the larvae. The results contribute to the understanding of ES2 as a promising alternative biopesticide, providing insights for future research and innovative applications in sustainable pest management strategies.

Detection of L1014F knockdown resistance mutation in Culex tritaeniorhynchus populations

Culex tritaeniorhynchus is a major Japanese encephalitis virus vector distributed in Southeast Asia and surrounding countries. The aim of the present study is to investigate insecticide resistance status among 10 Cx. tritaeniorhynchus populations of the Mediterranean region of Turkey. Bioassay results indicated that all of the populations were resistant or at least possibly resistant to 1,1′-(2,2,2-Trichloroethane-1,1-diyl) bis (4-chlorobenzene) (DDT) (4%), [(dimethoxyphosphorothioyl) sulfanyl] butanedioate, Diethyl (malathion) (5%), and 2-[(Propan-2-yl) oxy] phenyl methylcarbamate (propoxur) (0,1%). Whereas, some of the populations were still susceptible to 3-Phenoxybenzyl (1RS)-cis, trans-3-(2,2-dichlorovinyl)-2,2-dimethyl cyclopropane carboxylate (permethrin) (0,75%) and (S)-Cyano (3-phenoxy phenyl) methyl (1R,3R)-3-(2,2-dibromoethen-1-yl)-2,2-dimethylcyclopropane-1-carboxylate (deltamethrin) (0,05%). Biochemical analysis results showed altered alpha esterase, beta esterase, para-nitrophenyl acetate (PNPA), and glutathione-s-transferase (GST) levels in some populations while all of the populations had increased oxidase levels except for the Yumurtalık population. Additionally, all of the populations had sensitive acetylcholinesterase (AChE) levels similar to the control group except for the Erzin population. Correlation analysis showed a significant correlation between mortality rates for deltamethrin and alpha esterase, beta esterase, PNPA, and GST levels while mortality rates for permethrin were significantly correlated with GST levels. An allele-specific polymerase chain reaction (AS-PCR) detected high L1014F allele frequency in the populations. Overall results indicate the urgent need for monitoring and mapping of insecticide resistance in Cx. tritaeniorhynchus populations of the study area for effective vector control management.

Organophosphate Resistance in Aedes aegypti: Study from Dengue Hemorrhagic Fever Endemic Subdistrict in Riau, Indonesia.

Dengue hemorrhagic fever (DHF) is a significant health problem. The high number of cases requires preventions, including controlling the dengue vector, Aedes aegypti mosquito. One of the control methods is the use of insecticides containing organophosphate. This study aims to detect organophosphate resistance in Aedes aegypti from DHF endemic subdistrict, Riau, Indonesia by a sensitivity test of temephos and 5% malathion and measuring the activity of non-specific alpha and beta esterase enzymes. This observational study determined Aedes aegypti resistance from larvae to adult in one DHF endemic subdistrict in Riau, Indonesia. The bioassay was used for temephos sensitivity of Aedes aegypti larvae. The LC99 value was analyzed using probit and compared with the diagnostic value from WHO. The WHO susceptibility test was conducted to determine 5% malathion resistance from adult mosquitoes. The mortality of less than 90% was declared as resistant. Measurement of alpha and beta esterase levels used Lee's microplate assay technique based on visual identification and absorbance value (AV). The results showed that Aedes aegypti were resistant to temephos. It also showed that adult mosquitoes were resistant to 5% malathion. Based on the alpha esterase activity test, it was found that most of the mosquitoes showed very sensitive meanwhile, based on the beta esterase activity test, most of the mosquitoes were moderate resistance. This study suggests that Aedes aegypti population from DHF endemic subdistrict in Riau, Indonesia are indicated to develop resistance to organophosphate.

Characterization of Pyrethroid Resistance Mechanisms in Aedes aegypti from the Florida Keys.

ABSTRACTThe status of insecticide resistance in Aedes aegypti is of concern in areas where Aedes-borne arboviruses like chikungunya, dengue, and Zika occur. In recent years, outbreaks involving these arboviruses have occurred, for which vaccines do not exist; therefore, disease prevention is only through vector control and personal protection. Aedes aegypti are present on every inhabited island within the Florida Keys. The resistance status of Ae. aegypti in the Florida Keys was assessed to guide knowledge of the best choice of chemical for use during an outbreak. Mosquito eggs were collected using ovitraps placed on Key West, Stock Island, Vaca Key, Upper Matecumbe Key, Plantation Key, and Key Largo. Bottle bioassays were conducted at the Florida Keys Mosquito Control District using Biomist® 30+30 (Clarke Mosquito Control Products, Inc., Roselle, IL). Further bottle testing using malathion and permethrin occurred at the CDC, Fort Collins, CO, in addition to molecular and biochemical assays. Levels of resistance varied between islands with different underlying mechanisms present. Resistance was seen to Biomist® 30+30 but not to permethrin, indicating that piperonyl butoxide (PBO) or the inert ingredients may be involved in resistance. No study has been conducted to date examining the role of PBO in resistance. Key Largo was treated the most with adulticides and expressed the highest levels of alpha and beta esterases, oxidases, glutathione-S-transferases, and frequency of the V1016I knockdown mutation from all sites tested. Knowledge of localized resistance and underlying mechanisms helps in making rational decisions in selection of appropriate and effective insecticides.

Do mangrove habitats serve as a reservoir for Medicopsis romeroi, a clinically important fungus

Medicopsis romeroi is one of the frequent pathogens causing subcutaneous infections in immunocompromised patients. In this study, a sexual morph of Medicopsis romeroi was found on a decaying woody stem of the mangrove plant Suaeda monoica and its asexual morph was produced on malt extract agar. The sexual morph connection was established based on both morphological data and multigene phylogenetic analyses. Neomedicopsis chiangmaiensis comb. nov. is proposed by transferring Medicopsis chiangmaiensis to the genus Neomedicopsis based on morphology and multigene phylogenetic analyses. The preliminary pathogenicity tests on Medicopsis romeroi strain demonstrated beta haemolysin and esterase activities, and its ability to grow at 37 °C. It also exhibited strong activity in in vitro tests for aspartyl proteases, extracellular phospholipase, lipase and chitinase and mild activity for amylase and urease suggesting that this strain of Medicopsis romeroi, isolated from a mangrove habitat, could be an opportunistic pathogen to immunocompromised patients.

Effects of some Insecticide Mixtures on Toxicity and Some Biochemical Parameters of Cotton Leafworm, Spodoptera littoralis (Boisd.)

This study was evaluated the toxicity of three insecticides contains two effective substances, chlorpyrifos & lufenuron (Tempo XL), lufenuron & emamectin benzoate (Heater) and thiamethoxam & chlorantraniliprole (Folliam Felixi) against the 2nd and 4th larval instars of S. littoralis under semi-field condition in tomato field Ismailia Governorate during 2018 & 2019 seasons and assessing their biochemical effect against treated larvae. In laboratory results indicated that Heater had the highest efficacy against 2nd and 4th larval instars, with LC50 of 0.041 and 0.135 ppm for 2nd and 4th larval instars, respectively, followed by Folliam Felixi with LC50 of 0.076 and 0.233 ppm and finally Tempo XL with LC50 of 0.097 and 0.411 ppm for 2nd and 4th larval instars, respectively. Under the semi-field condition observed that the initial effect during 2018 & 2019 seasons, Heater proved to be the most effective and had the highest corrected larval mortality, while the general mean of residual activity was more than 90% in all treatments. In biochemical studies, alpha and beta esterases were the highest activities in S. littoralis larvae treated with tested compounds compared to untreated. The highest enzyme activity of acetyl- cholinesterase, acid and alkaline phosphatase was observed in Tempo XL, while in the case of Heater and Folliam Felixi there was no significant difference between them. The results also showed that with all treatments there was a significant decrease in the total protein.

Biological, biochemical and genotoxic effects of Sb in the midge Chironomus sancticaroli Strixino and Strixino, 1981 (Diptera: Chironomidae)

In aquatic systems, antimony (Sb) is found in the water column and associated with sediment particles being bioavailable to organisms. Consequently, toxic effects have been detected in benthic invertebrates, but the toxicity after Sb exposure in Chironomidae have not been investigated. Were investigated DNA damage, activities of cholinesterase (ChE), alpha and beta esterase (EST-α, EST-β), glutathione S-transferase (GST), catalase (CAT), and superoxide dismutase (SOD) and lipid peroxidation after acute (48 h) and subchronic exposure (8 d). We also investigated the effects of subchronic (8 d) on development of larvae and chronic (25 d) Sb exposure on emergence and size of adults of Chironomus sancticaroli. Were analyze Sb nominal concentrations ranged from 0.5 to 800 μg.L−1. Genotoxic effects occurred at higher concentrations upon acute (50, 800 μg.L−1) and subchronic exposure (50 μg.L−1). Acute exposure increased ChE, EST-α, EST-β, and GST activities. Subchronic Sb exposure increased EST-α activity at 0.2 μg.L−1 and GST activity at 5 μg.L−1. CAT activity increased at all concentrations while increasing lipid peroxidation levels were observed (1 μg.L−1, 5 μg.L−1 and 50 μg.L−1), indicating oxidative stress. All concentrations of Sb delayed larval development and decreased the number of emerging adults. At high concentrations (50, 500, 800 μg.L−1), the emerging adults were smaller. In conclusion, these varying genotoxic, biochemical and biological effects of Sb make a notable impact on the reproduction and population dynamics of C. sancticaroli.

Effects of phenanthrene on different levels of biological organization in larvae of the sediment-dwelling invertebrate Chironomus sancticaroli (Diptera: Chironomidae)

The hydrocarbon phenanthrene is an organic compound commonly found in the environment. In aquatic ecosystems, it is highly toxic to organisms, although little is known about its effects on sediment-dwelling organisms. The purpose of this study was to evaluate phenanthrene effects on biochemical, histological, and ontogenetic levels in larvae of the sediment-dwelling invertebrate Chironomus sancticaroli at acute and chronic exposure. Lethal concentrations were estimated and toxicity (acute-96 h and chronic- 8 d) tests were performed at phenanthrene concentrations from 0.12 to 1.2 mg L−1. At acute and chronic exposure, we evaluated acetylcholinesterase (AChE), alpha esterase (EST-α), and beta esterase (EST-β) activities as well as histological alterations. In the assays with chronic exposure, effects on larval development were estimated using antennae length (instar estimative) and body length (growth estimative). The EST-α showed a significantly increased activity after 48 h at acute exposure to high concentrations of phenanthrene, while EST-β activity was increased after 48 and 72 h at acute exposure at higher concentrations and at 0.12 mg L−1 at chronic exposure. At acute exposure, the midgut showed alterations such as brush border disruption, gastric caeca regression, and lumen area reduction; the fat body showed nuclear alteration in the trophocytes, while the Malpighian tubules showed brush border reduction and the salivary glands were subject to cytoplasm vacuolation. At chronic exposure, the same alterations were observed, in addition to vacuolar coalescence in the trophocytes of the fat body. Regarding larval development, a reduction of body length was observed with increasing phenanthrene concentrations. Similarly, molting was delayed; in the control group, all larvae were in the fourth instar, while at higher phenanthrene concentrations, larvae were predominantly in the third instar. Phenanthrene had toxic effects on this chironomid, indicating risks for natural populations.

Direct Effects of Temperature Changes on Biochemical and Enzymatic for Cotton Leafworm, Spodoptera littoralis (Boisd.)

It is important to understand the effects of increasing temperatures due to global warming on Egyptian cotton leafworm Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) which damages a wide variety of crops in the Middle East and is one of the major economic pests of cotton in Egypt. Therefore,we are investigating five different constant temperatures at 15, 20, 25, 30and 35oC as different thermal effects on biochemical parameters and enzymes of fourth larval instars. Biochemical analyses were performed to determine the effects of these different constant temperatures on the amount of total proteins, lipids, carbohydrates and free amino acids as well as metabolic, digestive, neural and detoxification enzymes. It's clear from the results that the total amount of proteins, free amino acids as well as, the activity levels of proteases were increased significantly by raising of temperatures to reach their maximum activities at 30oC. While the total amount of lipids, Carbohydrates were decreased significantly by raising of temperatures. Moreover, activity levels of amylase, invertase and Trehalase were decreased at 15oC.Amylase and invertase reached their maximum activity at 30oC,while Trehalase reached its maximum activity at 20oC. There was severe reduction in carbohydrate enzymes activities at 35oC. On other hands, the activity levels of total lipids and lipase were increased significantly at lower temperatures 15oC and 20oC, no significant changes were detected between other temperatures. The activity levels of GOT and GPT increased significantly and reached their maximum level at 20oC.However, GOT and GPT at other temperature were significantly different. The level of GST Enzyme was increased significantly at 30oC, while, its activity level was decreased at 15oC. Moreover, AchE, Alpha (EST-α) and beta esterase(EST-β) enzymes were increased gradually at 15,20 and 25 oC. They reached their maximum activities at 25oC followed by the reduction in activity levels at 30oC and 35oC.

Disruptive Effects of Selected Chitin Synthesis Inhibitors on Cotton Leaf Worm Spodoptera littoralis (Boisd.)

Spodoptera littoralis is one of the most devastating pests of cotton and other vegetables in Egypt as well as Mediterranean and middle east countries. Chitin synthesis inhibitors (CSIs) are quite distinctive in their mode of action and potentially act on the target species. The susceptibility of laboratory 2nd&4th instar larvae of cotton leafworm Spodoptera littoralis (Boisd.) to CSIs (Flufenoxuron, Chlorfluazuron and Triflumuron) was evaluated. The biochemical responses of S. littoralis larvae was detected using the lc50 of each compound. Flufenoxuron exhibited high level of toxicity with low LC50 value (0.069 ppm) followed by Chlorfluazuron (1.95 ppm) and then triflumuron (75.28) for the 2nd instar larvae while, the lc50 was (0.14 ppm) for flufenoxuron followed by 0.42 ppm for chlorfluazuron and then 1661.58 ppm for triflumuron with 4thinstar larvae. Second instar was more susceptible than the older ones except with chlorfluazuron the 4th instar more susceptible than the 2nd instar. Those CSIs exhibited variations of activities for each enzyme. Both of them increased the activity of AST (Aspartate Transaminase) on the contrary they decreased the activity of ALT (Alanine Transaminase). Flufenoxuron increased the activity of both alkaline phosphatase, alpha & beta esterases, chitinase and phenol oxidase, while it decreased the activity of acid phosphatase. Chlorfluazuron increased the activity of both alpha & beta esterases, chitinase and phenol oxidase, while it decreased the activity of both acid & alkaline phosphatases. Triflumuron increased the activity of both alpha esterase, acid phosphatase, chitinase and phenol oxidase, while it decreased the activity of both beta esterase and alkaline phosphatase. So, from this study, it can be concluded that the overall effects of CSIs use, including mortality and sublethal effects in insects, can facilitate the development of truly selective insecticides that can be employed in integrated pest management strategies.

ACTIVITY OF HYDROLYSIS ENZYMES IN DIFFERENT INSTAR LARVAE OF THE AMERICAN BOLLWORM, HELICOVERPA ARMIGERA (HUBNER)

Enzymes activity included acetylcholinesterase, non-specific α and β- esterases and alkaline phosphatase were determined calorimetrically in the whole homogenates of the different instar larvae; 3rd, 4th, 5th and 6th of the field strain as well as the baseline, laboratory strain of American bollworm, Helicoverpa armigera. The results indicated that the enzymes activity levels in the different instar larvae of the field strain were markedly higher than that in the laboratory strain at the respective instar larvae. The enzymatic activity levels increased steady from the 3rd to the 6th instar larvae. A sharp increase in the enzymatic activity levels were determined in the 6th instar larvae. The average levels of the enzymatic activity in both field colony and laboratory strain were 11.630 and 3.627 µg acetyl bromide released / min. /individual for A.Ch.E.; 8.819 and 3.430 µg α-naphthol released/ min/ individual and the corresponding values were ranged between 5.232 and 3.218 µg β– naphthol released / min/ larva for beta esterase; respectively and157.669 and 50.428 unit X 103/larva for alkaline phosphatase; respectively

Synergistic effect of certain insecticides combined with Bacillus thuringiensis on mosquito larvae

For effective vector control it is essential to formulate new preparations having multiple action against the vector pest. Developing combined formulation of biopesticide and chemical pesticide is one of the novel concept to fight against the vectors with new weapons; however, compatibility of biopesticide <em>i.e</em>. <em>Bacillus</em> <em>thuringiensis</em> (Bt) and chemical pesticide is a real hurdle. In this investigation, local isolate <em>Bacillus</em> <em>thuringiensis</em> SV2 (BtSV2) was tested for its compatibility with various available mosquito larvicides. Temephos was most compatible with BtSV2 than with other tested pesticides. These two compatible agents were tested for larvicidal potential. Our study revealed that the synergistic effect of both agents reduces LC50 value by 30.68 and 22.36% against the <em>Ae</em>. <em>aegypti</em> and <em>An</em>. <em>stephensi</em>, respectively. The larvicidal potential increased when compared to individual pesticides. It was also observed a biochemical change in larvae after the TBT (Temephos + Bacillus thuringiensis) combination treatment; it involves decreased level of alpha esterase, acetylcholine esterase and protein while level of beta esterase and acid phosphatase was unchanged and alkaline phosphatase activity was increased. Increased potential of combined formulation may be due to altered physiological condition.

Benzo(a)pyrene Exposure Causes Genotoxic and Biochemical Changes in the Midge Larvae of Chironomus sancticaroli Strixino & Strixino (Diptera: Chironomidae).

Benzo(a)pyrene (BaP) is a carcinogenic polycyclic aromatic hydrocarbon, also found in nature due to human activities. BaP adheres to sediments showing toxic effects on benthic organisms, including midge larvae of the family Chironomidae. We tested for toxic effects of benzo(a)pyrene on Chironomus sancticaroli Strixino & Strixino 1981 using biochemical and genotoxic biomarkers, to identify changes in metabolic and antioxidant pathways, besides neurotoxic and DNA damage. Enzyme activity was compared by exposing larvae to four nominal concentrations (0.47, 2.13, 3.41, and 4.73μgl-1) and DNA damage to two concentrations (0.47 and 4.73μgl-1), after exposure at 24, 48, 72, and 96h. BaP caused neurotoxic effect, showing acetylcholinesterase alterations at different treatments. Changes in the biotransformation pathway were detected, with an increased activity of alpha and beta esterase in 48h and reduction of glutathione-S-transferase activity in all periods at the highest concentrations. Damage to the antioxidant system was observed by the increase of the superoxide dismutase and reduction of the catalase, in 48h. Genotoxicity was detected by an increased DNA damage at 48 and 72h. The lowest concentration (0.47μgl-1), even presenting low mortality, also altered the biochemical parameters of the larvae. Thus, these results indicate that BaP causes metabolic, neurotoxic, and genotoxic effects on C. sancticaroli, even at low concentrations and short-term exposure. BaP can cause damage of immature invertebrates, and the ecological dynamics can be affected, since these organisms have trophic importance in the aquatic environment.

Polybrominated diphenyl ethers (PBDEs) effects on Chironomus sancticaroli larvae after short-term exposure

In-vivo effects of polybrominated diphenyl ethers (PBDEs) containing 3, 4 and 5 bromine atoms were tested on fourth-instar larvae of Chironomus sancticaroli (Diptera: Chironomidae) after 48h of exposure, by measuring the activity of the acetyl cholinesterase, alpha and beta esterases and glutathione S-transferase. The PBDE congeners 2,2′,4-triBDE (BDE-17), 2,2′,4,4′-tetraBDE (BDE-47) and 2,2′,4,4′,5-pentaBDE (BDE-99) were evaluated at 0.5, 1.0, 2.0 and 3.0ngmL−1. Acetyl cholinesterase activity decreased significantly (p≤0.05) at all evaluated concentrations of the three PBDE congeners, except for larvae exposed to BDE-17 at 1.0 and 2.0ngmL−1. The significant inhibition of acetyl cholinesterase activity ranged from 18% (BDE-47 at 0.5ngmL−1) to 72% (BDE-47 at 2.0ngmL−1). The enzymes alpha and beta esterase were also affected by the three congeners, reducing their activity from 14% (BDE-99 at 1.0ngmL−1) to 52% (BDE-47 at 2.0ngmL−1) and from 7% (BDE-99 at 2.0ngmL−1) to 34% (BDE-47 at 3.0ngmL−1) respectively. Substantial increments in glutathione S-transferase activity were similarly observed, varying from 138% (BDE-99 2.0 at ng mL−1) to 346% (BDE-17 at 1.0ngmL−1). DNA strand breaks were detected exclusively in larvae exposed to BDE-99 at 2.0 and 3.0ngmL−1 (H=11.7, p=0.019). These results showed that C. sancticaroli larvae were sensitive to the PBDEs treatments under the experimental conditions.

Biochemical effects of some insect growth regulators and bioinsecticides against cotton leafworm, Spodoptera littoralis (Boisd.)(Lepidoptera Noctuidae).

The current work was carried out to evaluate the biochemical effects of LC50 of four compounds; emamectin and spinetoram as bioinsecticides, hexaflumuron and teflubenzuron as Insect growth regulators (IGR’s) against the 4th instar larvae of Spodoptera littoralis to determine the effects of these compounds on total carbohydrates, proteins, lipids, acetylcholinesterase, chitinase, phenoloxidase, carbohydrates hydrolyzing enzymes, non-specific esterases, phosphatases and transaminase enzymes.The obtained results indicated that total proteins and lipids content were significantly decreased with all tested insecticides, except slightly increase in total protein with spinetoram, in contrast, all tested insecticides led to an increase in total carbohydrates. The tested insecticides significantly increased the invertase activity except emamectin decreased the enzyme activity. A significant decrease in the activity of trehalase and amylase activity was induced by the tested insecticides, except with emamectin and teflubenzuron in case of amylase. The tested insecticides significantly decreased the activity of acid (AcP) and alkaline (AlP) phosphates. It is clearly noticed that teflubenzuron and spinetoram significantly increased alpha esterases in contrast, decreased with hexaflumuron and emamectin. A highly significant decreased in beta esterases was induced by teflubenzuron and hexaflumuron and increased with spinetoram and emamectin. All tested insecticides induced a significant inhibitory effect on aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activity except with teflubenzuron.Acelylcolinesterase (AchE) activity significantly increased with emamectin and teflubenzuron while decreased with hexaflumuron and spinetoram. Phenoloxidase and Chitinase activity significantly increased with all tested insecticides.

Factors that alter the biochemical biomarkers of environmental contamination in Chironomus sancticaroli (Diptera, Chironomidae)

Changes in physiology of the nervous system and metabolism can be detected through the activity of acetylcholinesterase (AChE), alpha esterase (EST-α) and beta esterase (EST-β) in chironomids exposed to pollutants. However, to understand the real effect of xenobiotics on organisms, it is important to investigate how certain factors can interfere with enzyme activity. We investigated the effects of different temperatures, food stress and two steps of the enzymatic protocol on the activity of AChE, EST-α and EST-β in Chironomus sancticaroli. In experiment of thermal stress individuals from the egg stage to the fourth larval instar were exposed to different temperatures (20, 25 and 30°C). In food stress experiment, larvae were reared until IV instar in a standard setting (25°C and 0.9g weekly ration), but from fourth instar on they were divided into groups and offered different feeding regimes (24, 48 and 72h with/without food). In sample freezing experiment, a group of samples was processed immediately after homogenization and another after freezing for 30 days. To test the effect of centrifugation on samples, enzyme activity was quantified from centrifuged and non-centrifuged samples. The activity of each enzyme reached an optimum at a different temperature. The absence of food triggered different changes in enzyme activity depending on the period of starvation. Freezing and centrifugation of the samples significantly reduced the activity of three enzymes. Based on these results we conclude that the four factors studied had an influence on AChE, EST-α and EST-β and this influence should be considered in ecotoxicological approaches.

Low malathion concentrations influence metabolism in Chironomus sancticaroli (Diptera, Chironomidae) in acute and chronic toxicity tests

Low malathion concentrations influence metabolism in Chironomus sancticaroli (Diptera, Chironomidae) in acute and chronic toxicity tests. Organophosphate compounds are used in agro-systems, and in programs to control pathogen vectors. Because they are continuously applied, organophosphates often reach water sources and may have an impact on aquatic life. The effects of acute and chronic exposure to the organophosphate insecticide malathion on the midge Chironomus sancticaroli are evaluated. To that end, three biochemical biomarkers, acetylcholinesterase (AChE), alpha (EST-α) and beta (EST-β) esterase were used. Acute bioassays with five concentrations of malathion, and chronic bioassays with two concentrations of malathion were carried out. In the acute exposure test, AChE, EST-α and EST-β activities declined by 66, 40 and 37%, respectively, at 0.251 µg L-1 and more than 80% at 1.37, 1.96 and 2.51 µg L-1. In chronic exposure tests, AChE and EST-α activities declined by 28 and 15% at 0.251 µg L-1. Results of the present study show that low concentrations of malathion can influence larval metabolism, indicating high toxicity for Chironomus sancticaroli and environmental risk associated with the use of organophosphates.

Effect of different light regimes on esterase isozyme profiles of three species of Drosophila

Circadian rhythm has been identified in every organism studied, from unicellular marine algae to man, and in virtually all physiological and biochemical functions. The endogenous circadian system functions to organize behaviour and physiology to adapt to and anticipate environment changes in light and temperature. The present study is an attempt to understand enzyme profiles (alpha and beta esterases) of Drosophila melanogaster (Oregon-K strain), Drosophila gangotrii and Drosophila jambulina under light/dark (LD), continuous light (LL) and continuous dark (DD) conditions over 30 generations. A polyacrylamide gel electrophoresis (7.5% – native gel) was used to study the esterase isozyme banding patterns in three species of Drosophila. It has been noticed that there were three alpha esterase loci in Drosophila species which were designated as α-est 1, α-est 2 and α-est 3. Similarly there were three beta esterase loci which were designated as β-est 1, β-est 2 and β-est 3. Flies maintained in different light regimes showed differences in their allelic patterns with respect to alpha and beta esterases. It was observed that there was expression of some bands at a given light regime and the absence of the same in another regime. This shows that the different light regimes affect the expression of esterase isozymes.