MFO Enzyme Research Articles

Toxicity and sublethal effects of plant essential oils on life history and detoxification enzymes activity of two-spotted spider mite (Acari: Tetranychidae)

We studied the lethal and sublethal effects of essential oils (EOs) of Allium sativum L. and Vitex pseudo-negundo (Hausskn) on Tetranychus urticae Koch. Based on LC50 concentrations, A. sativum (19.2 µL/L air) was more toxic than V. pseudo-negundo (51.9 µL/L air). To assess the sublethal effects, adult mites were exposed to the LC10 and LC30 of each EO. Exposure to LC30 of A. sativum and V. pseudo-negundo negatively affected the development, survival, fecundity, and fertility of T. urticae F1 generation, as well as general esterase and MFO enzymes activity. These concentrations affected the detoxification enzyme activity of treated mites.

Aedes aegypti(Linnaeus) larvae from dengue outbreak areas in Selangor showing resistance to pyrethroids but susceptible to organophosphates

The resistance status of Selangor Aedes aegypti (Linnaeus) larvae against four major groups of insecticides (i.e., organochlorines, carbamates, organophosphates and pyrethroids) was investigated. Aedes aegypti were susceptible against temephos (organophosphate), although resistance (RR50 = 0.21–2.64) may be developing. The insecticides susceptibility status of Ae. aegypti larvae were found heterogeneous among the different study sites. Results showed that Ae. aegypti larvae from Klang, Sabak Bernam and Sepang were susceptible against all insecticides tested. However, other study sites exhibited low to high resistance against all pyrethroids (RR50 = 1.19–32.16). Overall, the application of synergists ethacrynic acid, S.S.S.- tributylphosphorotrithioate and piperonyl butoxide increased the toxicity of insecticides investigated. However, the application failed to increase the mortality to susceptible level (>97%) for certain populations, therefore there are chances of alteration of target site resistance involved. Biochemical assays revealed that α-esterase, (Gombak, Kuala Langat, Kuala Selangor and Sabak Bernam strains) β-esterase (Klang and Sabak Bernam strains), acetylcholinesterase (Kuala Selangor and Sabak Bernam strains), glutathione-S-transferase (Kuala Selangor and Sabak Bernam strains) and mono-oxygenases (Gombak, Hulu Langat, Hulu Selangor and Kuala Langat strains) were elevated. Spearman rank-order correlation indicated a significant correlation between resistance ratios of: DDT and deltamethrin (r = 0.683, P = 0.042), cyfluthrin and deltamethrin (r = 0.867, P =0.002), cyflyuthrin and lambdacyhalothrin (r = 0.800, P =0.010), cyfluthrin and permethrin (r = 0.770, P =0.015) deltamethrin and permethrin (r = 0.803, P =0.088), propoxur and malathion (r = 0.867, P = 0.002), malathion and temephos (r = 0.800, P = 0.010), etofenprox and MFO enzyme (r = 0.667, P =0.050). The current study provides baseline information for vector control programs conducted by local authorities. The susceptibility status of Ae. aegypti should be monitored sporadically to ensure the effectiveness of current vector control strategy in Selangor.

Cytochrome P450-Dependent Mixed Function Oxidases (MFO) System Dynamics During the Poly Aromatic Hydrocarbon (PAH) Metabolism in Green MusselPerna Viridis(Linnaeus, 1758)

Polyaromatic hydrocarbons (PAH's) are the prominent and most common pollutants in aquatic environments, particularly in marine water. The discharge of hydrocarbons into the sea might be of great concern for marine species living close to dumping sites. Therefore, toxicological properties of hydrocarbons released into marine environments need to be evaluated. PAH pollution potential may be predicted by assessing the induction of hepatic cytochrome P450-associated enzyme activity. The inducibility and activity of phase I reduction nicotinamide adenine dinucleotide phosphate, reduced (NADPH) cytochrome c reductase (CCR), cytochrome c oxidase (COX) and three CYP450 isoforms (benzyloxyresorufin - O-dealkylase [BROD], ethoxyresorufin-O-dealkylase [EROD] and methoxyresorufin-O-dealkylase [MROD] ) enzymes were measured in the hepatic S9 fraction prepared from Perna viridis collected from three sites: a highly oil-polluted site (Kasimedu fishing harbor, Rayapuram, Chennai [Station1]); a moderately polluted off-shore site, about 3 Km away from this area [Station 2]; and the least oil-polluted site (Vellar estuary, Parangipettai [Station 3], which was a reference site.) The levels of BROD (CYP2B6), MROD (CYP1A2) and EROD (CYP1A1) in the tissues of green mussel were measured using Spectro-Fluorometer SL-174, (ELICO, India). All the MFO enzymes exhibited a hierarchical dose-dependent activity in response to oil pollution in these study areas. Samples from the heavily oil-polluted (Kasimedu Station-1 and Station-2) areas exhibited greater activity of all enzymes than the least oil-polluted (Vellar estuary) reference area. Among the enzymes analyzed, the MROD activity was best correlated with the level of hydrocarbon contamination (P < 0.05). Therefore MROD can be considered as a robust biomarker for petroleum hydrocarbons in P. viridis.

Modification of pesticide toxicants Actara, Desis and Fabcosidine for larvae of Khabra Trogoderma granarium beetle with Prenobyl Piotoxide and phenobarbital

This study was designed to evaluate the toxicities of Actara, Decis and Vapcocidin and the effects of the mixed-function oxidase (mfo) enzymes inhibitor, piperonyl butoxide (pb ), and inducer, Phenobarbital (phb ), on the toxicities to the 15 2nd, 3rd, 4th and 51h instar larvae of Trogoderma granarium, using the impregnated filter paper technique. Based on the 24h LC50 values, the three insecticides were highly toxic to the larvae. Decis was about twice as toxic as Actara and both were greatly much more toxic than Vapcocidin. The toxicities of the three insecticides, generally, decreased as the Larval stage advanced (LC50 values in the 5- Larval instars were 1.7, 1.8, 2.2, 2.6, 3.1 0 l/filter paper, respectively, for Decis, 3.0, 3.5, 4.5, 6.0, 7.0 0 1/filter paper, respectively, for Actara and 6.0, 8.0, 11.0, 13.0, 15.0 0 1/filter paper, respectively, for Vapcocidin) and it is considered most likely that the decrease is due to the increase in the mfo enzymes activity. The mfo enzymes modifiers data showed that pband pbb greatly increased and decreased, respectively, the toxicities of the three insecticides. The date also revealed that mfo insecticide detoxifing enzymes activity increased as the Larval stage advanced. The studysuggests that Actara would be an effective alternative to pyrethroids against this insect.

Bioaccumulation of benzo(a)pyrene from sediment by fathead minnows: effects of organic content, resuspension and metabolism.

The accumulation of 14C-benzo(a)pyrene (BaP) sorbed to sediment was examined in fathead minnows (Pimephales promelas) to compare uptake from sediment with a high organic carbon (OC) content (7.7%), to that with a low OC content (2%). Ingestion of sediments was quantified by co-labeling the sediment with 141Cerium, which was not assimilated by the fish. Results of this study indicated that (1) significantly greater quantities of BaP were dissolved in water over low-OC sediment, compared to water over high-OC sediment, (2) fish disturbed the sediment and increased the concentration of BaP in centrifuged (particle-free) water, (3) fish ingested significantly more of the low-OC sediment than high-OC sediment, perhaps in response to the lower food quality of the low-OC sediment, and (4) uptake of BaP from sediment ingestion contributed <3% of the total flux of BaP into the fish. Primarily as a result of the greater concentration of BaP in water, fish from the low-OC exposures had significantly higher rates of BaP accumulation. However, after 48 h the body burdens in these fish declined by 50%, likely due to the induction of MFO enzymes in response to accumulation of BaP. A smaller effect was apparent in the fish from the high-OC exposures, consistent with the lower dose of BaP they experienced. These results illustrate the complex, and sometime counterintuitive, interactions that affect the uptake and bioaccumulation of sediment-associated contaminants.

Evaluation of environmental levels and biological impact of TBT in Malta (central Mediterranean)

Chemical monitoring for butyltins in bulk seawater, surface microlayer and superficial sediments determined that the two main local sources of marine contamination by tributyltin (TBT) compounds in Malta are ship-repairing dockyards and marinas. In bulk seawater, TBT values ranged from below the detection limit of 5 ng Sn l −1 to 300 ng Sn l −1; in sediments derived from the most polluted areas, TBT concentrations as high as 1500 ng Sn g −1 were measured. At TBT levels found in local harbours, several sublethal biological responses are possible and were observed, including a significant reduction in MFO enzyme system activities of fish; digestive cell atrophy in the oyster Ostrea edulis; and induction of imposex in the snail Hexaplex trunculus. The latter two responses are evident at TBT concentrations below the environmental quality standard (20 ng TBT l −1). The ecological implications of these results are discussed and it is concluded that exposure of marine organisms to TBT in local harbours may be expected to lead to a reduction in the long-term survival of a number of such organisms. For these reasons, both the use of TBT-based antifouling paints for pleasure boats as well as drydock practices need to be controlled by appropriate regulations and their enforcement.

Metabolism of 3H-retinol by lake trout ( Salvelinus namaycush) pre-exposed to 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126)

To provide insight into retinoid metabolism in fish exposed to polychlorinated biphenyl (PCB), juvenile lake trout were orally exposed to 0, 3, 10 or 30 μg 3,3′,4,4′,5-pentachloro-biphenyl (PCB 126) kg −1 body weight for 12 weeks. Phase I (MFO) enzyme activity was induced by 60, 177 and 450 fold, while glucuronyltransferase enzyme activity was 2.3, 2.5 and 5 fold higher in the 3, 10 and 30 μg PCB kg −1 dose groups, respectively, compared with untreated fish. After 12 weeks, cannulae were inserted into the dorsal aorta. Two days later, 3H-retinol was injected as a bolus in charcoal stripped plasma through the cannula. Blood samples were obtained 15 and 30 min and 1, 3, 6, 15, 30, 50 and 75 h after the injection. The radioactivity recovered from plasma was compared for each PCB dose group and was not significantly different for any of the treatments at any of the sample times. However, greater radioactivity recovered from bile after 75 h indicates accelerated metabolism of 3H-retinol with increasing PCB dose. Tissue distributions of aqueous and lipophilic soluble radioactivity indicates that direct metabolism of retinol by MFO and conjugation enzymes is probably responsible for the depletion of retinoids in PCB 126 exposed lake trout.

Baseline studies in the Slave River, NWT, 1990–1994: Part III. MFO enzyme activity in fish

As part of the Slave River Environmental Quality Monitoring Program, a background data set of baseline concentrations was collected for various environmental components including fish, water, bottom sediment, and suspended sediment. Fish collections included a serics of hepatic MFO analyses on walleye, northern pike, lake whitefish, and burbot. The EROD and AHH activity and P450 levels of fish, as well as weight, length, age, condition factor, and liver and gonadal somatic indices are described. Levels of EROD and AHH activity were of an order of magnitude expressed by the following relationship: walleye > northern pike > burbut > lake whitefish. Males consistently showed higher EROD, AHH activity and cytochrome P450 content relative to females of the same species even at control sites. Physical parameters varied very little within sites and exhibited some differences with the reference sites. A good MFO data set was collected for walleye and northern pike, but limited conclusions were possible with the lake whitefish and burbot data due to the overlap of sampling with the spawning season. Hepatic MFO enzyme activity indicated that some differences were evident in fish sampled from the Slave River relative to background/reference lakes; however, in many cases no differences were observed. Five years of biochemical effects studies have determined that the Slave River had low levels of induction suggesting a relatively pristine environment. This is further supported by the water, sediment, and body burden chemistry components of the Slave River Environmental Quality Monitoring Program.

Use of hepatic MFO and blood enzyme biomarkers in sand flathead ( Platycephalus bassensis) as indicators of pollution in Port Phillip Bay, Australia

Hepatic ethyoxycoumarin O-deethylase (ECOD) and ethoxyresorufin O-deethylase (EROD) activities, and serum sorbitol dehydrogenase (s-SDH) were measured over 3 years in sand flathead ( Platycephalus bassensis) collected from Port Phillip Bay, Australia. Significant enzyme induction generally occurred in regions closest to highly industrial and urbanized areas relative to undeveloped reference areas of the bay. High s-SDH levels were associated with lower hepatic microsomal ECOD and EROD levels. There were no sex differences in liver ECOD or s-SDH in any sampling period, and sex differences in EROD activity were only significant in September 1990, when males had significantly higher activities than females (47.0 pmol min −1 mg protein −1 compared with 28.4 pmol min −1 mg protein −1, respectively). Liver EROD activity in sand flathead from Hobsons Bay was positively correlated with total freshwater input, mainly from the Yarra River, suggesting PAHs as a possible cause of the observed induction.

Induction of mfo enzymes and production of bile metabolites in rainbow trout (Oncorhynchus mykiss) exposed to waste crankcase oil

It is difficult to assess the toxicological significance of complex mixtures of contaminants in the environment because of paucity of dose-response studies. Rainbow trout (Oncorhynchus mykiss) were exposed per os to waste crankcase oil and analyzed for hydrocarbon classes, 26 polycyclic aromatic compounds (PACs) and 66 elements. MFO enzyme activity, measured as 7-ethoxyresorufin O-deethylase (EROD) was induced in liver, kidney, and heart. The threshold level for induction in liver was approximately 3 mg of PACs (sum of 26 PACs) per kilogram fish. A dose-response relationship was obtained for liver and kidney but not for the heart. In a time-response study, liver, kidney, and heart MFO activity increased (14-, 5-, and 3-fold, respectively), reaching a maximum between days 1 and 4, then decreased to basal levels by day 12. Analysis of bile metabolites, as gluc-uronide and sulfate conjugates, showed a pattern similar to that displayed by MFO induction, possibly with a slight delay. This study establishes time- and dose-response relationships for MFO enzyme induction and appearance of bile metabolites in fish exposed to an environmentally important source of PACs.

Carcinogen-induced tissue vitamin A depletion. Potential protective advantages of beta-carotene.

Exposure to benzopyrene, an enzyme-inducing PAH carcinogen, promotes vitamin A depletion in exposed tissues. This effect is evident while on a vitamin A sufficient diet and without a decline in serum retinol. The finding of local tissue vitamin depletion without systemic depletion may have considerable implications in maintaining tissue health. While the described studies involved dietary exposure to benzopyrene, it is reasonable to extrapolate that inhalation exposure via cigarette smoke would have a similar effect in the lungs and perhaps stomach and bladder. Higher MFO enzyme activity in the lungs may have detrimental effects. Kellermann's early work identifying a higher incidence of lung cancer in those with genetically greater aryl hydrocarbon hydroxylase activity was interpreted as due to the greater formation of a reactive intermediate in the process of carcinogen metabolism. As an alternative hypothesis I suggest that those with higher enzyme inducibility may have greater carcinogen-induced vitamin A depletion. If poor tissue vitamin A nutriture potentiates the carcinogenicity of compounds such as benzopyrene, dietary or pharmacologic interventions which improve tissue nutriture could be important. The demonstrated effect of dietary beta-carotene on preventing carcinogen-induced tissue vitamin A depletion suggests one mechanism by which beta-carotene may be cancer protective. Further investigations are warranted, particularly with inhalation exposure to carcinogens and the effect of dietary beta-carotene on lung tissue nutriture.

Inheritance of metabolic resistance to the synthetic pyrethroids in Australian Helicoverpa armigera(Lepidoptera: Noctuidae)

AbstractTwo strains of Helicoverpa armigera (Hübner), resistant to synthetic pyrethroids, were isolated from field populations collected in the irrigated cotton growing areas of northern New South Wales: an isofemale strain, Mfo, and a composite field strain, Field. A series of crosses were undertaken between the Mfo and susceptible strains to determine the genetic basis of the resistance. Dose-responses were obtained by bioassay using topical application of fenvalerate in acetone. Considerable variation in tolerance was observed in both resistant and susceptible strains. In the Mfo strain, the major shift in resistance phenotype (33-fold resistance) was due to a single major gene with incomplete dominance. The resistance phenotype was not diluted by 23 generations of backcrossing. The major resistance phenotype could be eliminated almost completely by the addition of piperonyl butoxide which affects oxidative breakdown of the pyrethroids by mixed function oxidase (mfo) enzymes. Similar results were observed in the Field strain. Monitoring for resistance in field populations will be imprecise because a true discriminating dose does not exist for susceptible and heterozygous resistant individuals.

Mixed-function oxygenase enzymes as tools for pollution monitoring: Field studies on the french coast of the Mediterranean sea

1. 1. MFO enzyme activities were measured in microsomes from whole mussels ( Mytilus galloprovincialis) comber livers ( Serranus cabrilla), or Posidonia oceanica etiolated tissues, and PAH contents were determined in sediments collected in coastal locations of the French Riviera and Corsica during 3 oceanographic cruises in 1987–1988. 2. 2. BaP activities in mussel and EROD activities measured in fish were strongly correlated to the log of PAH content in sediments. The first results for CA4H in Posidonia showed significant differences related to PAH pollution levels. The increase in MFO activities measured in Corsica in summer 1988 indicated a recent petroleum contamination.

Participation of lipid peroxidation in the loss of hepatic drug-metabolizing activities in experimental fascioliasis in the rat

Fascioliasis causes a dramatic decrease in drug-metabolizing ability of the hepatic monooxygenase (MFO) and glucuronosyltransferase (GT) enzyme systems in the rat. The present study was undertaken to determine whether lipid peroxidation is involved in the enzymatic loss. Peroxidative damage of membrane lipids (as assessed by the tissue content of malonic dialdehyde, MDA, and the diene conjugation absorption in microsomal membranes) was found to occur over the entire course of the liver infection (concomitant to a decrease in glutathione levels), and to different degrees in relation to the various steps of the parasite cycle. The onset (MDA six times the controls; ΔE 1% = 1·55 at the 20th day) coincides with the beginning of the loss of MFO (− 30%) and GT (− 20% at the 20th day), and peaks between the 30th and 40th day (MDA eight times the controls; ΔE 1% = 1·96), when the loss in the enzyme activities is maximal (MFO − 60 70% ; GT- 65 95% ). There was a strict correlation at all the observation times between the extent of lipid peroxidation and the decrease in drug metabolizing ability: this supports the view that lipid peroxidation is the major agent in the impairment of MFO and GT enzyme activities, and very likely in the initiation of the pathological degeneration of the liver tissue. As evidenced by histological examination, the phagocytic response of the liver tissue to the parasite invasion and growth leads to oxidative stress, which is the causative agent in the initiation and development of lipid peroxidation.

Potentiation of aflatoxin B1 induced hepatotoxicity in male Wistar rats with ethanol pretreatment.

The interaction of ethanol and aflatoxin B1 (AFB1)-induced hepatotoxicity was studied in male Wistar rats using the activity of plasma GOT and GPT, liver triglyceride and histopathologic changes of liver necrosis as indices. Pretreatment of four oral doses of ethanol (4.0 g/kg BW each) at 48, 45, 24 and 21 hrs prior to AFB1 (0.5 to 2.0 mg/kg BW) single i.p. administration caused a significant increase in the activity of PGOT (6 folds) and PGPT (5 folds), liver triglycerides (2 folds) and severity of liver necrosis at 48 hrs after AFB1 administration. Ethanol pretreatment potentiated AFB1-induced hepatotoxicity by increasing MFO enzymes, aniline hydroxylase and p-nitroanisole-O-demethylase activity and lipid peroxidation, and decreasing in cytochrome b5, epoxide hydrolase activity and hepatic glutathione content. However, it did not cause any significant change in the activity of NADPH-cytochrome c reductase and glutathione-S-transferase and cytochrome P-450. These results suggest that potentiation of ethanol pretreatment on AFB1-induced hepatotoxicity may be due to an increase in the metabolic formation of AFB1-2, 3-oxide and subsequent binding to DNA.

Rotenone tolerance in mosquitofish

Resistant mosquitofish showed a 1·8-fold tolerance to rotenone over a susceptible strain. The 24-h LC 50 values for rotenone in susceptible and resistant mosquitofish were 0·017 ppm and 0·031 ppm, respectively. Results with sesamex, an inhibitor of mixed-function oxidase (mfo) enzymes, indicated that rotenone tolerance in mosquitofish is solely the result of increased levels of mfo enzymes.

A useful electron tube manual regulator : P.H. Craig ( Power Plant Engineering, Vol. 34, No. 6)

Chemical monitoring for butyltins in bulk seawater, surface microlayer and superficial sediments determined that the two main local sources of marine contamination by tributyltin (TBT) compounds in Malta are ship-repairing dockyards and marinas. In bulk seawater, TBT values ranged from below the detection limit of 5 ng Sn l−1 to 300 ng Sn l−1; in sediments derived from the most polluted areas, TBT concentrations as high as 1500 ng Sn g−1 were measured. At TBT levels found in local harbours, several sublethal biological responses are possible and were observed, including a significant reduction in MFO enzyme system activities of fish; digestive cell atrophy in the oyster Ostrea edulis; and induction of imposex in the snail Hexaplex trunculus. The latter two responses are evident at TBT concentrations below the environmental quality standard (20 ng TBT l−1). The ecological implications of these results are discussed and it is concluded that exposure of marine organisms to TBT in local harbours may be expected to lead to a reduction in the long-term survival of a number of such organisms. For these reasons, both the use of TBT-based antifouling paints for pleasure boats as well as drydock practices need to be controlled by appropriate regulations and their enforcement.