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Host blood meals and chromosomal inversion polymorphism in Anopheles arabiensis in the Baringo District of Kenya.

Studies were carried out in the villages of Kapkuikui and Maji-Ndege in the Loboi area of Baringo District, Kenya, to obtain baseline data on species identification of the Anopheles gambiae group, their feeding and resting behavior, and their frequencies of chromosomal inversions. This was carried out towards predicting the effect of introducing permethrin-impregnated cloths or other intervention measures. In this study, Anopheles arabiensis was identified as the only species of the An. gambiae group. This species contained 2 inversions, 2Rb and 3Ra, occurring at frequencies ranging from 55 to 60%, and from 5 to 11%, respectively. There was no evidence for nonrandom mating. Indoor- and outdoor-collected samples were significantly different in respect of inversion 3Ra in one village and in the distribution of the different sources of blood meals in both areas. In these villages, 37% of indoor-resting mosquitoes fed outside before entering houses to rest.

Animals↗

Malathion resistance in mosquitoes from Charleston and Georgetown counties of coastal South Carolina.

Susceptibility tests were conducted using the World Health Organization diagnostic test procedure on strains of Aedes taeniorhynchus, Aedes sollicitans, Aedes vexans, and Culex nigripalpus collected from several localities in Charleston and Georgetown counties of South Carolina. Aedes taeniorhynchus was resistant to malathion (mortality 1.0-54.4%) but not to propoxur, permethrin, or fenitrothion. There also were indications that Ae. sollicitans and Cx. nigripalpus were resistant to malathion, but to a lesser extent than Ae. taeniorhynchus (mortalities: 72.1-81.0%, and 46.2%, respectively). Aedes vexans was susceptible to malathion (mortality 98.6%). In field tests using ULV application of malathion and field-collected Ae. taeniorhynchus, and susceptible Ae. aegypti and Ae. taeniorhynchus, a noticeably lower mortality also was obtained in the wild mosquitoes.

Aedes↗

[Susceptibility of Anopheles gambiae to insecticides in the Ivory Coast].

Studies on the susceptibility of Anopheles gambiae to insecticides were carried out in rice field areas of Côte-d'Ivoire. An. gambiae larvae populations from Côte-d'Ivoire were resistant to DDT but susceptible to organophosphorous insecticides. Adult populations from the surroundings of Bouake were resistant to DDT and permethrin. Resistance to propoxur was strongly suspected. The knock-down effect of both deltamethrin and lambdacyhalothrin was delayed and strongly decreased. The control strain from Bobo-Dioulasso and populations from rice fields of Katiola located far from the city were still susceptible to the three pyrethroids. It is likely that resistance to pyrethroids in Bouake has been promoted by the intensive use of domestic aerosol sprays.

Animals↗

[The insecticidal activity of the new combined dust Malcord].

A formulation of 0.5% Malcord dust, which contains carbofos and permethrin (a 1:1 ratio) as active agents, was designed and examined. LC99 against synanthropic insects by the active ingredient was 0.01-0.005 g/m2. The effective application rate of the dust ranged 5 to 10 g/m2 in the treatment of various objects. The residual insecticidal effect of the dust on the treated surfaces remained 1.5-2.0 months (depending upon the type of an object). The dust Malcord has been permitted by the health care authorities of the Russian Federation for its usage by specialists and the population.

Animals↗

Insecticide susceptibility of Aedes aegypti and Aedes albopictus in the Lower Rio Grande Valley of Texas and Mexico.

In response to a potential dengue fever outbreak in south Texas during 1995, the susceptibilities of Aedes aegypti and Aedes albopictus to commonly used mosquito adulticides were assessed. Larvae collected from the Lower Rio Grande Valley of Texas and Mexico were reared to adults and tested against susceptible laboratory strains at Texas A&M University. Resistance ratios at both the LC50 and LC95 rates were all less than 10, indicating that adult populations of both species are still susceptible to malathion, chlorpyrifos, resmethrin, and permethrin.

Aedes↗

Field trial efficacy of two formulations of Permanone against Culex quinquefasciatus and Anopheles quadrimaculatus.

Tests were conducted during the summer of 1996 to evaluate the effectiveness of different formulations of permethrin, Permanone 31-66 and Aquareslin, against Anopheles quadrimaculatus and Culex quinquefasciatus. Tests of both formulations were conducted at rates of 2.019 and 3.926 g AI/h with each formulation/rate replicated 3 times. Results indicate significantly greater control of both pest species at the higher application rate for both formulations. The high rate of Permanone 31-66 proved more effective than that of Aquareslin. Exposure at the low rate for both formulations provided inadequate adult control that was particularly pronounced against Cx. quinquefasciatus. Regardless, negligible recovery of exposed adults was observed at any formulations/rate. No significant differences in mortality were noted for any formulation/rate relative to distance downwind. However, volume median diameter and droplets/cm2 were significantly affected by distance downwind. Furthermore, volume median diameter and droplets/cm2 were both determined to significantly affect mortality in both mosquito species (P < or = 0.05). Overall, results indicate that Permanone 31-66 and Aquareslin applied at a rate of 3.926 g AI/h were effective.

Animals↗

Comparative in vitro pediculicidal efficacy of treatments in a resistant head lice population in the United States.

OBJECTIVE: To compare the pediculicidal activity of 5 head lice products available in the United States on head lice from south Florida. DESIGN: In vitro pediculicidal product comparison. SETTING: Lice Source Services, Inc, located in Plantation, Fla, a clinic for the treatment and grooming of individuals with pediculosis capitis. PARTICIPANTS: Head lice were collected from healthy clients with Pediculus capitis that came to Lice Source Services, Inc, to seek their services. INTERVENTIONS: Within 2 to 6 hours of capture, lice were placed in continuous direct contact with the pediculicide products and observed at regular intervals. Results were compared with findings of a recent study of a treatment-sensitive population of head lice conducted in Panama. MAIN OUTCOME MEASURE: Percentage of lice dead at regular observation intervals between 5 minutes and 3 hours of continuous exposure to the pediculicides. RESULTS: Two prescription products, Ovide lotion (0.5% malathion) and 1% lindane shampoo, were ranked in the same order as in 2 previous studies (first and last, respectively). The order of effectiveness from most to least effective was as follows: Ovide lotion, A-200 shampoo (a natural pyrethrin product synergized with piperonyl butoxide), undiluted Nix (1% permethrin), diluted Nix, RID (a natural pyrethrin product synergized with piperonyl butoxide), and 1% lindane shampoo. CONCLUSIONS: There were statistically significant differences in the efficacy of all the products when compared with the results found in the recent study in Panama, except for Ovide lotion. Of those tested, Ovide was the only pediculicide in the United States that had not become less effective. The difference in efficacy of 1% lindane, Nix, and pyrethrins between the Panama and Florida studies supports the argument that some head lice in the United States have become resistant to these treatments.

Adult↗

Capillary electrophoresis of pesticides: V. Analysis of pyrethroid insecticides via their hydrolysis products labeled with a fluorescing and UV absorbing tag for laser-induced fluorescence and UV detection.

Some representative standard pyrethroid insecticides, namely permethrin, phenotrin, cypermethrin, sanmarton and fenpropathrin, were subjected to base hydrolysis with the aim of facilitating the indirect determination of these neutral species of low water solubilities by aqueous capillary electrophoresis. This first involved the base fragmentation of the pyrethroids in alcohol buffer (pH 12.0), and then the selective tagging of the carboxylated hydrolytic products with 7-aminonaphthalene-1,3-disulfonic acid (ANDSA) via a condensation reaction in the presence of organic soluble carbodiimide. The tagging of the hydrolytic products with ANDSA imparted each of the derivatives with two strong sulfonic acid groups whose permanent charges were necessary for achieving aqueous capillary electrophoresis. In addition, the labeling with ANDSA allowed the detection of the derivatives at low levels by capillary electrophoresis laser-induced fluorescence. The geometric and optical isomers of the ANDSA derivatives of the pyrethroid hydrolytic products were best separated when using electrolyte systems composed of sodium phosphate buffer, pH 6.5, containing n-octylglucoside chiral surfactant in the presence of small amounts of acetonitrile (e.g., 10% v/v).

Electrophoresis, Capillary↗

Pesticide-induced complete and partial chromosome loss in screens with repair-defective females of Drosophila melanogaster.

Commercial preparation of fungicides (captan and maneb), herbicides (bromacil, paraquat, picloram, and 2,4-D), and insecticides (carbaryl, chlorpyrifos, dimethoate, DDT, diazinon, carbofuran, and permethrin) were tested for their ability to induce complete and partial chromosome losses in Drosophila melanogaster males. In an attempt to identify the mutagenic activity of pesticides that are toxic in low concentrations in Drosophila, these males were mated with mus-302 repair-defective females. The rationale for this mating scheme is based on the repair of genetic damage in Drosophila sperm by maternal enzymes in the zygote, and on the reports that there may be increases in the frequency of recovery of chemically induced chromosome losses in crosses of treated males with mus-302 females. Verification of the sensitivity of this screen in this study came from significant increases in the frequency of chromosome loss induced by low concentrations of the positive controls, N-nitrosodimethylamine and methyl methanesulfonate. Of the 13 pesticides, the insecticide chlorpyrifos induced a significant amount of ring-X chromosome loss. No pesticide induced a significant increase in partial chromosome loss. These results are discussed in relation to the usefulness of repair-defective mutants in screens for genetic damage in Drosophila and other higher eukaryotes by chemicals that are toxic or cause sterility at low concentrations.

Animals↗

DNA-based genotyping techniques for the detection of point mutations associated with insecticide resistance in Colorado potato beetle Leptinotarsa decemlineata.

Three DNA-based genotyping techniques, bi-directional PCR amplification of specific allele (bi-PASA), single-stranded conformational polymorphism (SSCP) and minisequencing, have been developed and compared for the detection of the S291G (insensitive acetylcholinesterase) and L1014F (insensitive sodium channel) mutations associated with azinphos-methyl and permethrin resistance, respectively, in the Colorado potato beetle (Leptinotarsa decemlineata). Extraction of genomic DNA from individual neonates that were hatched from previously collected egg masses is the most efficient and reliable means to obtain suitable templates in terms of convenience, economy, speed and DNA quality. Bi-PASA, employing two allele-specific primers, appears to be the most efficient and rapid genotyping method for the simultaneous detection of both resistant/susceptible homozygous (SS, RR) and heterozygous (SR) alleles. Its resolution, however, is strongly dependent on the quality of template genomic DNA. SSCP also allows unambiguous genotyping, including the detection of heterozygous alleles, and is less dependent on template DNA quality, but requires a longer processing time. Minisequencing is amenable to a 96-well microtiter plate format for the processing of a large number of samples and allows direct detection of resistant/susceptible homozygous alleles but is not as efficient as the PASA and SSCP in detecting heterozygous alleles. In considering the advantages and disadvantages of each technique, DNA-based genotyping is best employed in combinations, with the bi-PASA as the primary method and the SSCP and minisequencing as the secondary validating methods. These methods are rugged, rapid, cost-effective and capable of resolving SS, RR and SR individuals. The availability of such DNA-based genotyping techniques, using neonate genomic DNA as templates, will enable the precise monitoring of the resistant and susceptible allele frequencies, including those of heterozygote individuals, in field populations of L. decemlineata.

Acetylcholinesterase↗

The molecular interactions of pyrethroid insecticides with insect and mammalian sodium channels.

Recent progress in the cloning of alpha (para) and beta (TipE) Na channel sub-units from Drosophila melanogaster (fruit fly) and Musca domestica (housefly) have facilitated functional expression studies of insect Na channels in Xenopus laevis oocytes, assayed by voltage clamp techniques. The effects of Type I and Type III pyrethroids on the biophysical properties of these channels are critically reviewed. Pyrethroid resistance mutations (termed kdr and super-kdr) that reduce the sensitivity of the insect Na channel to pyrethroids have been identified in a range of insect species. Some of these mutations (e.g. L1014F, M918T and T929I) have been incorporated into the para Na channel of Drosophila, either individually or in combination, to investigate their effects on the sensitivity of this channel to pyrethroids. The kdr mutation (L1014F) shifts the voltage dependence of both activation and steady-state inactivation by approximately 5 mV towards more positive potentials and facilitates Na channel inactivation. Incorporation of the super-kdr mutation (M918T) into the Drosophila Na channel also increases channel inactivation and causes a > 100-fold reduction in deltamethrin sensitivity. These effects are shared by T929I, an alternative mutation that confers super-kdr-like resistance. Parallel studies have been undertaken using the rat IIA Na channel to investigate the molecular basis for the low sensitivity of mammalian brain Na channels to pyrethroids. Rat IIA channels containing the mutation L1014F exhibit a shift in their mid-point potential for Na activation, but their overall sensitivity to permethrin remains similar to that of the wild-type rat channel (i.e. both are 1000-fold less sensitive than the wild-type insect channel). Mammalian neuronal Na channels have an isoleucine rather than a methionine at the position (874) corresponding to the super-kdr (M918) residue of the insect channel. Replacement of the isoleucine of the wild-type rat IIA Na channel with a methionine (I874M) increases deltamethrin sensitivity 100-fold. In this way, studies of wild-type and mutant Na channels of insects and mammals are providing a molecular understanding of kdr and super-kdr resistance in insects, and of the low pyrethroid sensitivity of most mammalian Na channels. They are also giving valuable insights into the binding sites for pyrethroids on these channels.

Animals↗

Estrogenic and antiprogestagenic activities of pyrethroid insecticides.

Many pesticides possess hormonal activity and have thus been classified as endocrine disruptors. Pyrethroids are commonly used insecticides worldwide, but little has been done to characterize their hormone agonist/antagonist potential. We tested four frequently encountered pyrethroids, fenvalerate, sumithrin, d-trans allethrin, and permethrin, for estrogen and progesterone agonist/antagonist activities using the Ishikawa Var-I human endometrial cancer cell line and the T47D human breast cancer cell line. Both cell lines produce alkaline phosphatase as an indicator of hormonal activity. Fenvalerate and sumithrin demonstrated significant estrogenicity; at concentrations of 10 microM, these compounds achieved maximal activities comparable to that of 10 nM 17alpha-ethynylestradiol in Ishikawa Var-I cells. None of the four compounds showed statistically significant estrogen antagonist activity or acted as progestins. However, fenvalerate and d-trans allethrin significantly antagonized the action of progesterone in T47D cells. Through these hormonal pathways, exposure to certain pyrethroids may contribute to reproductive dysfunction, developmental impairment, and cancer.

Alkaline Phosphatase↗

Effects of pesticides on DNA and protein of shrimp larvae Litopenaeus stylirostris of the California Gulf.

Recently, diverse pathologies and massive mortalities have been presented in shrimp hatcheries located along the California Gulf; therefore, toxic responses of shrimp larvae were used as biomarkers of pesticide pollution, because in this region intensive agriculture is practiced. Shrimp larvae were exposed to DDT, azinphosmethyl, permethrine, parathion, chlorpyrifos, malathion, endosulfan, and carbaryl, in order to determine LC50, DNA adducts and/or breaks, and total protein in larvae. The results indicate reductions in protein and DNA in larvae exposed to these pesticides, and in those exposed to DDT, breaks and/or adducts were registered. It is possible that pesticide pollution is a cause of these problems, because reduction in protein indicates a decrease in larvae growth rate and DNA breaks or adducts have been related to pathologies and carcinogenesis in many aquatic organisms.

Animals↗

Effects of selected neuroactive chemicals on calcium transporting systems in rat cerebellum and on survival of cerebellar granule cells.

This investigation examined the relationship between alteration of Ca(2+)-transport systems and cytotoxicity in vitro for a number of neuroactive chemicals including environmental pollutants. 45Ca2+ uptake as a measure of Ca2+ sequestration was determined in mitochondria and microsomes isolated from cerebella of adult male Long-Evans hooded rats by differential centrifugation. Ca2+ extrusion, measured as Ca(2+)-ATPase activity, was determined in synaptosomes prepared by sucrose density gradient. Cytotoxicity (lactate dehydrogenase leakage) was assessed in primary cultures of cerebellar granule cells from 6- to 8-day-old Long-Evans rats. N-Methyl-D-aspartic acid (NMDA) did not alter synaptosomal Ca(2+)-ATPase activity or 45Ca2+ uptake in mitochondria and microsomes. However, chlorpromazine (CPZ), aluminum (Al), permethrin (PER), and deltamethrin (DEL) inhibited Ca2+ sequestration by mitochondria and microsomes. The IC50 values (microM) for CPZ, Al, PER, and DEL were 67.8, 671, 4.2, and 91.2 for mitochondrial 45Ca2+ uptake, and 129.9, 1384, > 50, and > 200 for microsomal 45Ca2+ uptake, respectively. CPZ, PER, and DEL also inhibited synaptosomal Ca(2+)-ATPase activity in a concentration-dependent manner with IC50 values of 62.5, > 400, and 246.9 microM, indicating an effect on the Ca(2+)-extrusion process. Al increased Ca(2+)-ATPase activity (EC50 = 833 microM). Although NMDA did not inhibit Ca(2+)-transport systems, it was cytotoxic at 250 microM and higher concentrations after 2 hr of exposure. Similarly, CPZ was cytotoxic at concentrations of 25 and 10 microM after 4 hr exposure. However, PER, DEL, and Al were not cytotoxic at any concentration up to 500 microM. Of all the chemicals tested, CPZ was the most potent in inhibiting Ca(2+)-transporting systems and was also cytotoxic.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum↗

Insecticide and Insecticide Metabolite Interactions with Cytochrome P450 Mediated Activities in Maize

In vitro assays were used to determine if organophosphate, carbamate, and synthetic pyrethroid insecticides affected the cytochrome P450 monooxygenase (P450) catalyzed hydroxylation of nicosulfuron, bentazon, cinnamic acid, or lauric acid in maize microsomes. All P450 activities were inhibited approximately 50% by carbaryl, and none were inhibited by permethrin. Hydroxylations of nicosulfuron, bentazon, lauric acid, and cinnamic acid were inhibited by malathion 83, 92, 38, and 0%, respectively. Terbufos was only moderately (36%) inhibitory of in vitro P450 hydroxylation of nicosulfuron. Nicosulfuron hydroxylation was more sensitive than bentazon hydroxylation to inhibition by the insecticides, and both herbicide hydroxylations were more sensitive than lauric acid or cinnamic acid hydroxylations to the insecticides. Since the oxidative metabolites of terbufos were shown to be more potent inhibitors of in vivo nicosulfuron metabolism than terbufos, we examined the effect of terbufos-sulfone on in vivo and in vitro herbicide metabolism. Terbufos-sulfone inhibited metabolism of nicosulfuron and imazethapyr, but not bentazon, in excised corn shoots. Microsomal hydroxylation of nicosulfuron, bentazon, chlorimuron ethyl, and imazethapyr, as well as the desulfuration of malathion, were strongly inhibited (>65%) by terbufos-sulfone. Cinnamic acid hydroxylase appeared to be different from the P450(s) responsible for the pesticide metabolism as it was not inhibited by terbufos-sulfone. However, the data also suggest that malathion, nicosulfuron, bentazon, chlorimuron ethyl, and imazethapyr all share a P450 in common with terbufos-sulfone. Alternatively, there may be separate P450s for the metabolism of the herbicides and malathion, all of which also metabolize terbufos-sulfone. These data show that the inhibition of P450 hydroxylation of nicosulfuron by terbufos-sulfone can explain the injury when maize is exposed to both terbufos and nicosulfuron. However, the insecticides that are the most potent in vitro P450 inhibitors are not necessarily the ones that cause the most herbicide injury in the field.

Journal Article↗

Differences in the neuroexcitatory actions of pyrethroid insecticides and sodium channel-specific neurotoxins in rat and trout brain synaptosomes.

The effects of pyrethroid insecticides and other sodium channel-specific neurotoxins on synaptosomal membrane potential were investigated in rat and trout brain synaptosomes using the membrane-permeant lipophilic cation [3H]tetraphenylphosphonium (TPP+). Concentration-dependent and tetrodotoxin-sensitive decreases in TPP+ accumulation, indicative of membrane depolarization, were produced by veratridine, aconitine, scorpion (Leiurus quinquestriatus) venom, and type I and type II pyrethroids, in both species. Veratridine, aconitine, and Leiurus venom were more potent and efficacious membrane-depolarizing agents in rat synaptosomes than in trout synaptosomes. Type II (deltamethrin, cypermethrin) pyrethroids produced similar depolarizing responses in rat and trout synaptosomes; however, the 1R-cis-alpha R isomer of deltamethrin, which had no effect on membrane potential in rat synaptosomes, depolarized trout synaptosomes. This isomer of deltamethrin was also shown to produce toxicity in trout, but not in rats. The type I pyrethroids, permethrin and NRDC 157, exhibited significantly greater intrinsic activity in trout brain synaptosomes, producing maximal membrane depolarizations that were three times greater than those observed in rat brain synaptosomes. These results provide evidence of species-specific differences in the membrane-depolarizing properties of pyrethroid insecticides and sodium channel-specific neurotoxins. They also suggest that some of the neurotoxin binding domains of the voltage-sensitive sodium channel in trout brain differ from those in mammalian brain. The hypersensitivity of fish to the neurotoxic actions of pyrethroid insecticides may be related to these differences.

Alkaloids↗

Neurochemical effects of DDT in rat brain in vivo.

p,p'-DDT and related agents act to hold the sodium channel open once opened and this effect is believed to be responsible for neurological effects of tremor and hyperexcitability in vivo. There is a good correlation between DDT-induced tremor and an increase in the levels of the metabolites of norepinephrine (NE), serotonin (5HT) and, to a lesser extent, dopamine (DA) in the brain stem (BS), hypothalamus (HYP), striatum (STR), or hippocampus (HPC). DDT also increases levels of excitatory amino acids glutamate (GLU) and aspartate (ASP), but the effect occurs only in the brain stem. These effects are dose- and time-related. Pharmacological studies found that blockade of alpha 1-adrenergic receptors attenuate DDT-induced tremor, while blockade of serotonergic, cholinergic muscarinic, and dopaminergic receptors augment the toxicity of DDT. Tremor was almost completely blocked in rats pretreated with hydantoin, an anticonvulsant believed to block repetitive firing of nerves by interfering with the inactivation gate of the sodium channel. A similar antagonism was observed for permethrin, a Type I pyrethroid believed to have a mechanism of action very similar to that of DDT. However, hydantoin increased the tremorigenic effects of chlordecone, an organochlorine whose mechanism has not been linked to the sodium channel. These data are consistent with the hypothesis that the in vivo neurotoxicity of some organochlorine insecticides is related to their effects on the sodium channel.

Amino Acids↗

Susceptibility of the taiga tick Ixodes persulcatus Schulze to pyrethroids.

The susceptibility of the taiga tick Ixodes persulcatus Schulze to 15 pyrethroids has been evaluated. The knockdown time after exposure of ticks to pyrethroids tested was quite similar. It was revealed that the lethal doses of type I pyrethroids (permethrin-like) induced the rapid attachment of ticks to host. In contrast, the fatal poisoning with type II pyrethroids (alpha-CN-pyrethroids) made the ticks unable to attach completely. Possible mechanisms of the acceleration and the prevention of attachment are discussed.

Animals↗