Inhibitor Report for: Fenchlorphos

Ataxia-telangiectasia (A-T) is a neurodegenerative disease caused by mutation of the A-T mutated (ATM) gene. ATM encodes a protein kinase that is activated by DNA damage and phosphorylates many proteins, including those involved in DNA repair, cell cycle control, and apoptosis. Characteristic biological and molecular functions of ATM observed in mammals are conserved in Drosophila melanogaster. As an example, conditional loss-of-function ATM alleles in flies cause progressive neurodegeneration through activation of the innate immune response. However, unlike in mammals, null alleles of ATM in flies cause lethality during development. With the goals of understanding biological and molecular roles of ATM in a whole animal and identifying candidate therapeutics for A-T, we performed a screen of 2400 compounds, including FDA-approved drugs, natural products, and bioactive compounds, for modifiers of the developmental lethality caused by a temperature-sensitive ATM allele (ATM8) that has reduced kinase activity at non-permissive temperatures. Ten compounds reproducibly suppressed the developmental lethality of ATM8 flies, including Ronnel, which is an organophosphate. Ronnel and other suppressor compounds are known to cause mitochondrial dysfunction or to inhibit the enzyme acetylcholinesterase, which controls the levels of the neurotransmitter acetylcholine, suggesting that detrimental consequences of reduced ATM kinase activity can be rescued by inhibiting the function of mitochondria or increasing acetylcholine levels. We carried out further studies of Ronnel because, unlike the other compounds that suppressed the developmental lethality of homozygous ATM8 flies, Ronnel was toxic to the development of heterozygous ATM8 flies. Ronnel did not affect the innate immune response of ATM8 flies, and it further increased the already high levels of DNA damage in brains of ATM8 flies, but its effects were not harmful to the lifespan of rescued ATM8 flies. These results provide new leads for understanding the biological and molecular roles of ATM and for the treatment of A-T.

The development of chemical control of Musca domestica on Danish farms 1945--72 is outlined. It has been strongly influenced by successive development of resistance and failure of control by one insecticide after another. The chlorinated hydrocarbons used as residual sprays failed 1947--51. Organophosphorus compounds (OPC) were widely used from 1953, first as strips impregnated with parathion and residual sprays with diazinon. Resistance to OPC was first found in 1955, diazinon was given up in 1957--59 and parathion strips failed in the early '60's. Trichlorfon paint-on baits were widelyused 1958--64 and serious resistance did not appear until 1967, induced by selective pressure of fenthion and dimethoate used as residual sprays. High resistance to the contact effect of trichlorfon now occurs everywhere in Denmark. However, trichlorfon baits are still able to kill many flies. Residual sprays with fenthion, ronnel and fenitrothion were used to some extent 1960--70, but increased resistance reducing the residual effect developed in 2--3 years. Dimethoate was used on the majority of farms 1965--72. It was very effective the first years and resistance increased slowly until 1971--72, when high to extreme dimethoate-resistance became general on Danish farms. This was associated with high resistance to other OPC for fly control, e.g. fenthion, fenitrothion, bromophos, and tetrachlorvinphos, and to carbamates, with the result that no generally effective residual sprays were available. In 1971--72 frequent treatments with synergized pyrethroids have been tried. However, the method is often expensive, and serious resistance problems have appeared on a few farms. In this situation preventive, sanitary measures to eliminate or reduce fly breeding in manure are becoming decisive again, but difficult to practise due to lack of farm labour. The extreme Danish situation is compared with those in other areas, and probable reasons for differences in resistance and control problems are discussed, as well as possibilities for strategies to reduce resistance development.

The studies were carried out on mice between the 14th and 19th days, i.e., in the period of maximum penetration of T. spiralis larvae in the host's muscles. Phosphoro-organic esters were given orally to experimental animals in oil solution, at the following doses: Z-50 -- 150 mg per kg of body weight and Z-51 -- 100 mg per kg of body weight. The influence of esters on the activity of cholinesterases was investigated with the Koelle-Friedenwald method, modified by Gomori. The aim of the study was to establish the joint activity of the migrating Trichinella larvae and phosphoro-organic esters on the organism of the host. Z-50 and Z-51 penetrate in therapeutic doses the striated muscles rather weakly. 24 hrs after these compounds were given, acetylcholinesterase (AChE) activity was inhibited in motor end-plates in about 30%, and in muscle fibres infected with T. spiralis larvae in about 60-70%. Pseudocholinesterase (PChE) activity was stronger inhibited than AChE. 24 hrs after applying Z-50 and Z-51 PChE was inhibited in about 90%. Of the two phosphoro-organic esters being examined Z-51 stronger inhibited the cholinesterases activity than Z-50. It was found that the efficiency of phosphoro-organic esters in the course of trichinellosis depends on its ability of infiltration into the host's muscles and on the degree of inhibition of the active cholinesterases in the motor end-plates. Attention was drawn to the fact that increased activity of cholinergic system is one of the main factors in the patholgenesis of the second phase of trichinellosis, i.e., the migration and penetration of the larvae in the muscular fibres of the host.

Ataxia-telangiectasia (A-T) is a neurodegenerative disease caused by mutation of the A-T mutated (ATM) gene. ATM encodes a protein kinase that is activated by DNA damage and phosphorylates many proteins, including those involved in DNA repair, cell cycle control, and apoptosis. Characteristic biological and molecular functions of ATM observed in mammals are conserved in Drosophila melanogaster. As an example, conditional loss-of-function ATM alleles in flies cause progressive neurodegeneration through activation of the innate immune response. However, unlike in mammals, null alleles of ATM in flies cause lethality during development. With the goals of understanding biological and molecular roles of ATM in a whole animal and identifying candidate therapeutics for A-T, we performed a screen of 2400 compounds, including FDA-approved drugs, natural products, and bioactive compounds, for modifiers of the developmental lethality caused by a temperature-sensitive ATM allele (ATM8) that has reduced kinase activity at non-permissive temperatures. Ten compounds reproducibly suppressed the developmental lethality of ATM8 flies, including Ronnel, which is an organophosphate. Ronnel and other suppressor compounds are known to cause mitochondrial dysfunction or to inhibit the enzyme acetylcholinesterase, which controls the levels of the neurotransmitter acetylcholine, suggesting that detrimental consequences of reduced ATM kinase activity can be rescued by inhibiting the function of mitochondria or increasing acetylcholine levels. We carried out further studies of Ronnel because, unlike the other compounds that suppressed the developmental lethality of homozygous ATM8 flies, Ronnel was toxic to the development of heterozygous ATM8 flies. Ronnel did not affect the innate immune response of ATM8 flies, and it further increased the already high levels of DNA damage in brains of ATM8 flies, but its effects were not harmful to the lifespan of rescued ATM8 flies. These results provide new leads for understanding the biological and molecular roles of ATM and for the treatment of A-T.

Evaluation of a previously published gel permeation chromatographic (GPC) procedure was undertaken to determine whether it can be used for additional organochlorine pesticides. After repeatability studies of many pesticides, the following compounds were approved for inclusion in the U.S. Department of Agriculture Domestic Residue Monitoring Program: coumaphos-S, stirophos, chlorpyrifos, ronnel, carbophenothion, chlorfenvinphos, phosalone, kepone, captan, linuron, and endosulfan I and II. Recoveries ranged from 54% for captan to 123% for ronnel. Ranges of CVs varied from 0-9.5% for carbophenothion to 7.1-47.7% for kepone. Although the minimum acceptable recovery of 50% was attained for all 12 pesticides, the anticipated CV of 20% was waived to include chlorpyrifos, endosulfan I and II, and kepone. For a multiresidue procedure involving approximately 40 compounds, these results were within the acceptable criteria.

Ronnel [0,0-dimethyl 0-(2,4,5-trichlorophenyl) phosphorothioate] is an organophosphate pesticide with growth-promoting properties. Experiments were conducted to determine effects of ronnel on oxidation of and fatty acid synthesis from acetate and glucose as indices of metabolic activity in subcutaneous adipose tissue and skeletal muscle from 6-, 12- and 18-mo-old steers. Ronnel depressed metabolic activity in adipose tissue from 6- and 12-mo-old steers without concomitantly decreasing metabolic activity in skeletal muscle. Production of CO2 and fatty acids from acetate and glucose in tissues from 18-mo-old steers was influenced less by ronnel than in tissues from younger steers. Interactions of ronnel with thyroxine or growth hormone on acetate oxidation and conversion to fatty acids in adipose tissue also were investigated. Thyroxine increased acetate oxidation and decreased fatty acid synthesis. Ronnel interfered with the metabolic effects of thyroxine. Growth hormone, with or without ronnel, did not affect metabolic activity of adipose tissue. Ronnel seemingly alters the partitioning of acetate and glucose between major metabolic processes in adipose tissue and skeletal muscle.

An experiment with eight beef steers was conducted to determine the patterns of change for plasma concentrations of thyroxine (T4), triiodothyronine (T3), cholesterol and total lipid following the addition or withdrawal of the organophosphate, ronnel, from the diet. Steers were fed 0, 2, 4 and 8 mg ronnel/kg body weight daily in a Latin square arrangement of treatments with five 28-d periods. Plasma samples were obtained at -2, 1, 3, 5, 7, 9, 16 and 23 d of each period. Steers had not received ronnel before period 1 and, for periods 2 to 5, steers previously fed the lower levels (0 and 2 mg ronnel) were switched to the higher levels (4 and 8 mg ronnel) and steers previously fed the higher levels were switched to the lower levels. Treatment assignments for periods 1 and 5 were the same. Feed intake was similar for all treatments (7.8 kg/d) and daily gain was greater when ronnel was fed (.65 vs .88 kg). Plasma T4 concentrations increased positively in response to ronnel level within the first day after ronnel feeding began and reached a plateau within 3 d. Plasma T4 concentrations decreased following the withdrawal of ronnel, but the response was slower; a lower level being established within about 7 d. Changes in plasma T3 concentrations were small, but were concurrent with plasma T4 changes and were inversely related to ronnel level. Plasma cholesterol concentrations tended to be positively related to ronnel level, but changed slowly with time; plasma total lipid concentrations were not consistently affected by ronnel level. The results of this experiment demonstrate that ronnel has an immediate effect on thyroid function in beef steers.

Insecticidal formulations in the form of dusts or aerosols containing rotenone from the root of Derris elliptica and pyrethrum from the flower of Chrysanthemum cinerariaefolium are commonly used in homes and gardens. Ronnel (fenchlorphos), a systemic insecticide, is used to control house flies and, upon oral treatment, ectoparasites of cattle. These insecticides are extensively used and their teratologic potential has not been fully investigated. Technical grades of rotenone at 0, 2.5, 5, or 10 mg/kg, pyrethrum at 0, 50, 100, or 150 mg/kg (rotenone and pyrethrum were of natural origin) and ronnel at 0, 400, 600 or 800 mg/kg were tested. Each of these was suspended in corn oil and administered orally in single daily doses on d 6-15 of pregnancy to Wistar rats. The dams were killed on the last day of pregnancy, and all fetuses were evaluated following routine teratologic methods. Rotenone was associated with an increased number of nonpregnant rats and resorptions, at a dose of 10 mg/kg; reductions in maternal body weight gain, fetal weight, and skeletal ossification, together with an increased incidence of extra rib, were found at 5 and 10 mg/kg; but no significant effects were found at 2.5 mg/kg. Increases in the incidence of resorptions in pyrethrum-treated groups and of extra rib in ronnel-treated groups were also observed.

This paper describes the effect of the organophosphorus compound, the oxygen analogue of ronnel (OAR), on the activity of some membrane-bound enzyme systems in the brain mitochondria of developing, young-adult, and old rats. Age-related changes were noted in the cholesterol-to-protein ratio, whereas the phospholipid content in mitochondria showed little change during development as well as aging. The results obtained suggest that development of brain succinate dehydrogenase may consist in a decrease of Km and increase of Vmax values. In aged rats an altered, perhaps inhibited form of the enzyme is produced. The oxygen analogue of ronnel caused a mixed-type inhibition of the succinate dehydrogenase derived from brains of 4-day-old, 16-day-old and 2-month-old animals. In the case of enzyme from the brain of 18-month-old rats, a typical competitive-type inhibition was observed. Mechanisms responsible for inhibition of the succinate: cytochrome c reductase from brains of developing animals are similar to those for succinate dehydrogenase. In aged rats (18 months old), however, a noncompetitive mechanism of inhibition of succinate: cytochrome c reductase was revealed. The experiments reported here provide evidence that lipid-soluble molecules of OAR may interact with membrane phospholipids and lead to modification of membrane architecture and also of enzyme kinetic behaviour. It may be also concluded, that the sensitivity of the enzyme systems studied to inhibition by OAR is an age-dependent phenomenon. Modification of membrane by development or aging alters the kinetics as well as the sensitivity of enzymes to inhibitors.

Four feeding trials were conducted to determine (1) how the organophosphate ronnel affects thyroid and adrenal circulating hormone levels and blood profile measurements of beef steers and (2) whether the effects of ronnel observed in beef steers could be produced in growing rats. In trial 1, four groups of eight steers each were given either no ronnel or 4 mg ronnel/kg body weight daily in diets fed at either limited (1.8% of body weight) or ad libitum intake. After 7 weeks, intake levels, but not ronnel treatments, were reversed during a 1-week transition period, and feeding was continued for another 7 weeks. In trial 2, four groups of six steers each were given 0, 44, 88 or 176 ppm ronnel premixed in diets fed ad libitum for 18 weeks. Actual ronnel intakes averaged 0, 1.01, 2.12 and 4.73 mg/kg body weight daily in trial 2. In trials 3 and 4 , growth and intake were measured in 64 and 32 growing Sprague-Dawley rats, respectively, fed levels of ronnel ranging from 0 to 100 ppm in the diet. In trial 3, blood plasma was analyzed at various times for triiodothyronine (T3), thyroxine (T4), cholesterol and total lipid content. In trial 1, the concentration of Plasma T4 was 1.31 times higher in steers fed ronnel that in control steers. In trial 2, plasma T4 was 1.30 times higher in steers fed 176 ppm ronnel, the level that improved growth, than in steers fed the lower ronnel levels. Circulating levels of T3, cortisol and aldosterone were similar for both control and ronnel-fed steers. Serum cholesterol concentrations were consistently higher in ronnel-fed steers. The data indicated that the growth-promoting effect of ronnel in steers may be associated with a shift in thyroid function. Effects of ronnel in steers were not observed in rats, demonstrating a species difference between steers and rats.

The level of dermaphos residues in the blood, liver and the fat tissue was examined after a single oral application of the pure and technical preparation of various doses in hens and rabbits. An appropriately adapted method of extraction and purification and thin-layer chromatography for its quantitative determination were used. It was shown that the preparation, as well as some of its metabolites and contaminants had a tendency of prolonged accumulation in the examined tissue mainly in fat. A month after the administration of higher doses of pure dermaphos (i.e. 0,250 g/kg of body weight, calculated as active component) the blood of rabbits still contained 0,12 mg/kg, the liver--0,10 mg/kg, and the kidney fat--3,14 mg/kg of the preparation. In hens a dose of 2,500 g/kg of body weight gave the following results: 0,60 mg/kg in the blood, 0,67 mg/kg in the liver and 8,34 mg/kg in the omental fat. This long-lasting accumulation of dermaphos in the tissues is most probably connected with the presence of the trichlorphenyl ring in the molecule. It was also noticed that the contaminants present in the technical preparation influenced to some extent the accumulation rate of dermaphos in certain tissues and this was observed especially after administration of higher doses. On the other hand, the dynamics of disappearance and the accumulation degree of dermaphos in the hen and rabbit tissues did not depend only on the type of the tissue, but also on the animal species and the level of the administered dose.

A screening method has been developed for determining organophosphorus pesticides at ng/L levels in drinking water. Sixteen organophosphorus pesticides, diazinon, diazinon-oxon, dimethoate, ronnel, beta-phosphamidon, methyl parathion, ethyl parathion, malathion, chlorpyrifos, fenitrothion, ruelene, methidathion, ethion, EPN, phosalone, and phosmet, were extracted by Amberlite XAD-2 resin from 100 and 200 L drinking water previously spiked with these pesticides. The pesticides were eluted from the XAD-2 resin with acetone-hexane (15+85). The concentrated extract was analyzed by gas chromatography using a nitrogen-phosphorus selective detector and by gas chromatography-mass spectrometry using selected ion monitoring. Recoveries at the 10 and 100 ng/L spiking levels were greater than 90%, except recoveries for dimethoate and phosphamidon were 37 and 42%, respectively. The analysis of 300 L Ottawa tap water showed no detectable amounts (less than 1 ng/L) of any of the 16 organophosphorus pesticides.

The development of chemical control of Musca domestica on Danish farms 1945--72 is outlined. It has been strongly influenced by successive development of resistance and failure of control by one insecticide after another. The chlorinated hydrocarbons used as residual sprays failed 1947--51. Organophosphorus compounds (OPC) were widely used from 1953, first as strips impregnated with parathion and residual sprays with diazinon. Resistance to OPC was first found in 1955, diazinon was given up in 1957--59 and parathion strips failed in the early '60's. Trichlorfon paint-on baits were widelyused 1958--64 and serious resistance did not appear until 1967, induced by selective pressure of fenthion and dimethoate used as residual sprays. High resistance to the contact effect of trichlorfon now occurs everywhere in Denmark. However, trichlorfon baits are still able to kill many flies. Residual sprays with fenthion, ronnel and fenitrothion were used to some extent 1960--70, but increased resistance reducing the residual effect developed in 2--3 years. Dimethoate was used on the majority of farms 1965--72. It was very effective the first years and resistance increased slowly until 1971--72, when high to extreme dimethoate-resistance became general on Danish farms. This was associated with high resistance to other OPC for fly control, e.g. fenthion, fenitrothion, bromophos, and tetrachlorvinphos, and to carbamates, with the result that no generally effective residual sprays were available. In 1971--72 frequent treatments with synergized pyrethroids have been tried. However, the method is often expensive, and serious resistance problems have appeared on a few farms. In this situation preventive, sanitary measures to eliminate or reduce fly breeding in manure are becoming decisive again, but difficult to practise due to lack of farm labour. The extreme Danish situation is compared with those in other areas, and probable reasons for differences in resistance and control problems are discussed, as well as possibilities for strategies to reduce resistance development.

The effect of Fenchlorphos on postirradiation changes of serum protein levels and nucleic acid content in rat liver were investigated. It was found that this compound significantly decreases postirradiation changes in serum proteins, properdin level and nucleic acid content in rat liver. An important role of these phenomena in radioprotective action of Fenchlorphos is suggested.

The studies were carried out on mice between the 14th and 19th days, i.e., in the period of maximum penetration of T. spiralis larvae in the host's muscles. Phosphoro-organic esters were given orally to experimental animals in oil solution, at the following doses: Z-50 -- 150 mg per kg of body weight and Z-51 -- 100 mg per kg of body weight. The influence of esters on the activity of cholinesterases was investigated with the Koelle-Friedenwald method, modified by Gomori. The aim of the study was to establish the joint activity of the migrating Trichinella larvae and phosphoro-organic esters on the organism of the host. Z-50 and Z-51 penetrate in therapeutic doses the striated muscles rather weakly. 24 hrs after these compounds were given, acetylcholinesterase (AChE) activity was inhibited in motor end-plates in about 30%, and in muscle fibres infected with T. spiralis larvae in about 60-70%. Pseudocholinesterase (PChE) activity was stronger inhibited than AChE. 24 hrs after applying Z-50 and Z-51 PChE was inhibited in about 90%. Of the two phosphoro-organic esters being examined Z-51 stronger inhibited the cholinesterases activity than Z-50. It was found that the efficiency of phosphoro-organic esters in the course of trichinellosis depends on its ability of infiltration into the host's muscles and on the degree of inhibition of the active cholinesterases in the motor end-plates. Attention was drawn to the fact that increased activity of cholinergic system is one of the main factors in the patholgenesis of the second phase of trichinellosis, i.e., the migration and penetration of the larvae in the muscular fibres of the host.