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PubMed1986

Inhibition of gamma-aminobutyric acid-stimulated chloride flux in mouse brain vesicles by polychlorocycloalkane and pyrethroid insecticides.

Selected polychlorocycloalkane and pyrethroid insecticides were evaluated as inhibitors of gamma-aminobutyric acid (GABA)-dependent chloride flux into mouse brain vesicles. The inhibitory potencies of the polychlorocycloalkane insecticides, measured as concentrations producing 50% inhibition, spanned a 1200-fold concentration range in the following order of decreasing potency: 12-ketoendrin; isobenzan; endrin; dieldrin; heptachlor epoxide; aldrin; heptachlor; and lindane. For the cyclodienes, inhibition of chloride uptake was closely correlated with both mammalian toxicity and the ability to displace the binding of [35S]t-butylbicyclophosphorothionate (TBPS). However, lindane was much less potent as an inhibitor of GABA-dependent chloride uptake than would be expected from its acute toxicity or potency as an inhibitor of [35S]TBPS binding. Mirex and chlordecone were poor inhibitors of GABA-dependent chloride uptake, indicating that other sites are likely to be involved in their toxic action. The pyrethroid insecticide deltamethrin gave 50% inhibition of GABA-dependent chloride uptake at 25 microM, but the extent of inhibition was not increased at higher concentrations. In addition, the nontoxic enantiomer of deltamethrin produced dose-dependent inhibition in the chloride flux assay with a potency about 10-fold less than deltamethrin. These results demonstrate the utility of this functional assay to identify compounds that act at the GABAA receptor-ionophore complex and implicate this complex as the principal site of neurotoxic action for cyclodiene insecticides. Although lindane and deltamethrin also altered GABAA receptor-ionophore function, their low potencies and the incomplete stereospecificity of deltamethrin inhibition suggest that this complex is not involved in the neurotoxic action of lindane and alpha-cyano-substituted pyrethroids.

Animals↗

PubMedDate not supplied

[Current aspects of the problem caused by insecticide residues].

1. In Italy in recent years the use of pesticides in agriculture has increased considerably, especially with respect to organophosphate compounds. On the other hand, organochlorine insecticides now are less employed, because since 1970 laws have been introduced by which the use of these chemicals has been limited. Among the organochlorinated insecticides now employed, we find above all lindane, endosulfan and, in floriculture, DDT. The problem with the environmental diffusion and accumulation of organochlorine pesticides therefore is always related to the human long-term pathology, not yet definitively understood. Since the sixties we have given attention to the problems in the use of pesticides, with regard to organochlorine, we have been investigating either environmental pollution (surface and subsoil water, food, etc.) or human exposure to pesticide residues, whether direct or indirect. In 1968 we investigated, in an area of Tuscany given over to floriculture, the chlorinated insecticides blood levels in 46 exposed subjects (floriculturists) and in a control-group (50 subjects) who had only indirect exposure. We found high values in those of all kinds of the tested insecticides (lindane, aldrin, heptachlor epoxide, DDT) without observing any significant difference among the concentrations of the compounds analyzed in both groups. This showed that at that time the diffusion of organochlorine in the environment was such as to affect all people, independently of occupation, who thus were seen to have the some risk of exposure. 2. Twenty years later we carried out similar research in order to verify whether or not the laws previously referred to produced changes; we also wished to ascertain the possible amounts of the concentration of the pesticides in the blood. Therefore, following the some procedure employed in the previous research, we determined, by gascromatographic technique, pesticide levels (lindane, aldrin, heptachlor epoxide, DDT) in human blood from two different population groups coming from the some area of Tuscany. We analyzed blood drawn from 54 floriculturists (of both sexes aged from 18 to 71 years mean = 43.2 years- and with about 14 years of service on average) and 54 not-professionally exposed subjects, of both sexes, aged from 27 to 73 years (mean = 56 years). Our data have now been compared with those obtained from the study carried out in 1968. All the results have been statistically analyzed in accord with the Student's T-test.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗

PubMedDate not supplied

[The inheritance of irritability to insecticides in malarial mosquitoes].

Mosquito populations are not uniform in irritability to insecticides. Due to this reason presentation of the test results as an average number of one mosquito's flights during 10 or 15 minutes contact with insecticide paper does not reflect infrapopulation differences. It is proposed to divide mosquitoes into 3 groups: not irritable (0-1 flight per 10 minutes of contact), moderately irritable (2-9 flights), and highly irritable (10 and more). For the irritability tests only mosquitoes with 0-1 flight (during contact with control paper) were taken. Spontaneously irritable mosquitoes (2 and more flights in control) may become the reason of erroneous results. Yearly and seasonal changes of irritability level in different Anopheles species depending on the insecticide spraying intensity are shown. First proof of the inherited irritability to insecticides and specificity of this quality is obtained. Indirect data indicate that probably polygenic inheritance of irritability takes place in Anopheles.

Animals↗

PubMed1989

[The determination of toxicity of four insecticides on ground squirrel flea].

This paper reports the results of toxicological effect of four insecticides on Citellophilus tesquorum sungaris. The toxicity of Deltamethrin was the strongest in four insecticides, DDVP & DDT were stronger than 1-(3,4-dichlorophenyl)-2,2,2-trichloroethyl acetate. For the LD50 of four insecticides on suckling blood female flea of two-day-age, were 1.17 x 10(-6) micrograms per flea 1.20 x 10(-3) micrograms per flea 1.25 x 10(-3) micrograms per flea & 3.46 per flea respectively. The data showed that there were marked differences in the susceptibility to the same insecticide between unsuckling blood fleas and suckling blood fleas. Male fleas were more susceptible than female fleas in suckling blood fleas.

Animals↗

PubMed1988

Joint action of nuclear polyhedrosis virus and chemical insecticides against the black cutworm, Agrotis ipsilon (Hufn.).

A polyhedrosis virus disease was isolated from the larvae of Agrotis ipsilon. Isolation of causative agent from the infected larvae again showed to be positive. Microscopic examination of the infected larvae (by means of a light microscope) gave an evidence of the development of the polyhedral inclusion bodies (PIB) in all typical tissues where the virus is known to develop. Examination by an electron microscope showed various irregular shaped polyhedra; their diameter being about 1.5 to 3.5 mu. Most of these polyhedra were hexagonal and they measured about 2.2 mu. Experimental studies were conducted to investigate its pathogenicity alone and when combined with chemical insecticides. The joint action of the nuclear polyhedrosis virus of A. ipsilon (AINPV) combined with four chemical insecticides namely Fenvalerate, Decamethrin, Cypermethrin and Methomyl was assessed against the second instar larvae of A. ipsilon. Results showed that Decamethrin was the most toxic compound followed by Cypermethrin and Fenvalerate while Methomyl was the least toxic, the median lethal concentrations (LC50) were 0.25, 0.77, 14 and 450 ppm, respectively. The LC50 value of AINPV was 12 x 10(6) PIB/ml. Mixtures containing sublethal concentrations (LC25 and less) of both AINPV and any of the tested insecticides showed synergistic effects. On the other hand, an additive effect was observed with combinations containing doses of chemical insecticides over the range between LC25 and LC50 values.

Animals↗

PubMed1988

Decline of chlorinated hydrocarbon insecticides residues in the tea-garden soils of Taiwan.

Residues of chlorinated hydrocarbon insectidies and some of their metabolites, including p,p'-DDT, p,p'-DDD, p,p'-DDE, gamma-BHC, aldrin, dieldrin, heptachlor and heptachlor epoxide, were examined in the soils collected from 21 tea-gardens distributed in 15 countries of 6 prefectures in 1977, and from 100 locations distributed in 46 counties of 10 prefectures in 1984 in Taiwan. Although the use of these chlorinated hydrocarbon insecticides has been banned for many years, minor amounts of residues in the soils have still been detected. From 1977 to 1984, average residues of the chlorinated hydrocarbon insecticides and their metabolites in the soils of tea-gardens decreased from 5.64 to 0.06 ppb for gamma-BHC, 97 54 to 1.10 ppb for aldrin, 35.91 to 1.00 ppb for p,p'-DDE, 17.41 to 0.28 ppb for dieldrin, and 30.17 to 3.42 ppb for p,p'-DDT. But the number of positive cases increased for all chlorinated hydrocarbon insecticides tested, the residual levels were not significantly different among soils with different physiochemical properties or among soil layers. No significant amount of these insecticides was found in the processed tea.

Hydrocarbons, Chlorinated↗

PubMedDate not supplied

Effects of insecticide, diazinon, on pancreas of dog, cat and guinea pig.

The organophosphate insecticide Diazinon has been reported to cause acute pancreatitis in dogs. Based on histochemical examination of the acinar tissue, it was suggested that pancreatic tissue-fixed butyrylcholinesterase (BuChE) is the target enzyme of organophosphate toxicity. To further evaluate this theory, we exposed dogs, cats, and guinea pigs to a single sublethal dose of the organophosphate insecticide Diazinon (75 mg/kg). In cats, which lack pancreatic BuChE, no pathological changes occurred after two, three, and six hours, whereas in the guinea pigs as in dogs, both having abundant pancreatic BuChE, vacuolization of the acinar cells, interstitial edema and vasculitis indicate acute edematous pancreatitis as early as two hours. Atropine pretreatment (0.2 mg/kg) gave complete protection against pancreatitis. It was concluded that inhibition of pancreatic BuChe leads to cholinergic hyperstimulation of the acinar cell, which results in acute pancreatitis, and that pancreatic BuChE is essential for dogs and guinea pigs to downregulate cholinergic excitation. The insecticide pancreatitis model is considered a simple, non-invasive, reproducible, and cheap and useful method to evaluate early changes and methods of treatment in acute pancreatitis. Pancreatitis in humans has also been reported after accidental insecticide exposure.

Animals↗

PubMed1977

Organo-phosphorus insecticide poisoning-review of 53 cases.

A review of 53 cases of organo-phosphorus insecticide poisoning admitted to the department of intensive care at the Jinnah Postgraduate Medical Centre between 15th January to 31st December, 1976 has shown that these insecticides form a majority of the causes of acute poisoning and are associated with a comparatively high mortality rate. Out of a total of 157 cases of acute poisoning admitted to the department, 34% were cases of organo-phosphorus insecticide poisoning forming 13 5% of the total admissions. These insecticides being easily accessible, are frequently used as suicidal agents specially by uneducated housewives. They are highly toxic and their management is very complicated. Of a total of 15 deaths from poisoning, 11 (73%) were due to this cause. This being such a common mode of poisoning in our country, we have presented here our experience of the clinical features and management of these cases.

Adolescent↗

PubMed1965

Chlorinated insecticides in the body fat of people in India.

The storage of insecticides in the body-fat of persons has previously been studied in several countries (e.g., England, France, USA) and food has been shown to be the main source from which DDT and perhaps other insecticides are absorbed. In view of the differences in dietary habits in India, a study was made to determine whether there are differences in the storage of chlorinated hydrocarbon insecticides in persons in India from that in persons in other countries.It was found that civilians in the Delhi area with no occupational exposure to insecticides had a significantly greater deposit in their fat of DDT-related compounds and HCH than do comparable persons in the USA, but less dieldrin and heptachlor epoxide. Storage in military personnel in other Indian cities from which samples were obtained was similar to that in the USA for most DDT-related compounds and HCH but, as in Delhi, lower for dieldrin and heptachlor epoxide.

Adipose Tissue↗

PubMed1971

Rational design of insecticides.

A steric model of diaryl insecticides, which includes the structure of DDT and its analogues, was used for the synthesis of new highly active insecticides. The new compounds show low toxicity to mammals and their insecticidal activity can be potentiated by microsomal oxidase inhibitors. There is evidence that they readily undergo biological degradation. However, a spontaneous controlled chemical degradation was also established for the diaryl oxetanes, which form one group of a new series of insecticides. The theoretical model was further investigated using X-ray crystallography to establish one accurate structure. Biologically, the model is supported by studies of the correlation between insect mortalities and temperature and by measurements of nerve impulses at fly chemoreceptors after treatment with selected compounds.

Animals↗

PubMed1983

Factors influencing microbe insecticide interactions.

Microorganisms are present in almost all environmental components where insecticides are used and they will, therefore, encounter with the latter. In simplest terms, such interactions can be considered as (1) the action of microbes on insecticides and (2) the action of insecticides on microbes. These interactions can not be as clearly understood without understanding the influence of environmental factors that control the fate and activity of microorganisms. The proposed review will focus on two areas. The first is related to the test methods used to study the microbial insecticide interaction, the second area is concerned with the influence of environmental factors on the action of microbes and vice versa.

Bacteria↗

PubMed1983

Resistance to organophosphate and carbamate insecticides in Anopheles atroparvus.

Adult Anopheles atroparvus, from Cadiz, Spain (strain AT SPA) were resistant to several organophosphorus and carbamate insecticides. Separate lines of the AT SPA strain selected with propoxur, fenitrothion, fenthion and malathion were cross-resistant to these insecticides as well as chlorphoxim and bendiocarb. Lack of synergism between malathion and triphenyl phosphate (TPP), a carboxylesterase inhibitor and between fenitrothion and piperonyl butoxide (PB), a multi-function oxidase inhibitor, against the selected lines suggests that resistance to these insecticides may be non-metabolic. Lack of synergism of propoxur after 2 h exposure with PB, sensamex and SV1 (which all inhibit multi-function oxidases), may suggest that the same mechanism is involved here. However, all three synergists were effective in conjunction with 6 h exposure to propoxur. The postulated mechanisms are: a non-metabolic resistance, possibly an altered site of action, responsible for the non-synergizable resistance to organophosphorus insecticides and to a lesser extent the carbamates and a multi-function oxidase inhibitor-suppressed mechanism conferring resistance to propoxur.

Anopheles↗

PubMed1977

[Studies of the time of effectiveness and the characterization of compounds in insecticide tests with Aedes aegypti].

The contact-toxicity of 5 insecticides (2 chlorinated hydrocarbons, 2 organophosphate compounds 1 P-substance) are tested against Aedes aegypti L (adults). Because of the relationship between dosage (quantity of application) and time of effectiveness of a compound, we are able to design a specific curve of time-efficacy of each insecticide at graded intervals (= increasing dilutions). This curve may be characteristic of different pure compounds--possibly in connection with other features. The time measurement as a quantitative response was chosen according to the directions of Finney 1952 (mean time to response--dosage). The simple statistical analysis was possible after continuous observation until response-metameter as criterion for time of bioassay = time of exposure. Transformation into complete records (Finney) in feasible with a long period of observation, corresponding response-metameter, extreme values etc. This was found to be the only way to obtain a statistical analysis without complications, and only a few parameters in this model. For statistical evaluation of the differences of the mean reaction times for each dilution of DDT, gamma-BHC, Methylparathion and Trichlorofon the U-test according to Mann & Whitney has been applied. Percentages of 'inactivity' at each dilution are added (decreasing from D7). --The curve of time--efficacy is described, and the possibilities of characterization and indentification of the compounds discussed. General features of ET 50 values and mean reaction times are pointed out, and also the relation of time to response (= exposure time) and dosage, expressed by a simple hyperbolic equation (Haber's formula). The uptake of insecticides by "self-dosine" of insects (as practised in this bioassay) is the closest approximation to natural conditions, but the real dose is unknown [and will depend on the physiological condition of the insects]. Some values with Aedes aegypti (whole activity of the pure compound of each test object labelled with radioactive Trichlorfon) are added (exposure on 1 per cent deposite of insecticide).

Aedes↗

PubMed1981

Serum and red cell cholinesterase activity in people exposed to organophosphate insecticides.

Serum and red cell cholinesterase activities were determined in 2 groups of subjects namely:-I) a group of 10 patients who took organophosphate insecticide and were admitted into the hospital for treatment and II) a group of 65 workers from an organophosphate insecticide factory. Serum cholinesterase levels were considerably depressed in all patients in group I and one patient died. The low serum cholinesterase activities increased very slowly and were still very low on day 4 of admission. Serum cholinesterase level in 65 workers were significantly lower than that of the normal subjects. The exposed subjects had still further lower serum cholinesterase activity than those of the non-exposed subjects. There was no significant difference between their red cell cholinesterase activities and those of the normal subjects. Serum and red cell cholinesterase levels in these workers also showed no correlation to the duration of insecticide exposure. These findings indicated that serum cholinesterase activity was a good diagnostic aid in acute exposure because it responded more rapidly than red cell cholinesterase level but it was not sensitive for follow up of the treatment since its recovery rate was too slow. Findings of low serum cholinesterase with normal red cell cholinesterase levels without signs or symptoms of toxicity indicated that these workers had been exposed to some degree of organophosphate insecticides.

Adolescent↗

PubMed1978

The efficacy of various insecticides against the larvae of Lucilia cuprina (Wied.), the green blowfly of sheep. I. In vitro tests using a resistant and susceptible strain.

In order to determine the larvicidal action of different insecticides against both susceptible and resistant blowfly strains in the Republic of South Africa, an attempt was made to find a suitable in vitro method for mortality counts and potency evaluations. After a series of preliminary trials the Australian method of Roxburgh & Shanahan (1973) was adopted as the most reliable for this purpose. A statistical analysis by computer of the basic data at Onderstepoort established the superiority of the LC50 value in biological assays over the LC99 or the closely related minimum lethal concentration (MLC). The insecticidal action of different blowfly compounds was evaluated for relative potency against both susceptible and resistant blowfly strains by comparing their LC50 values in their logarithmic form. Comparisons are fully justifiable where the individual regression coefficients of the insecticides under test do not deviate significantly from a common slope initially calculated (Finney, 1971). A diazinon formulation proved the most potent against susceptible blowflies and fenthion ethyl against the resistant strain from Riversdale. Relative insecticidal potencies varied from 0,07-0,62 in the former compound and from 0,35-0,66 in the latter.

Biometry↗

PubMed1994

Financing mechanisms for village activities in The Gambia and their implications for financing insecticide for bednet impregnation.

The recent enthusiasm for impregnated bednets as a malaria control measure leaves unresolved the question of how to finance them. The National Impregnated Bednet Programme in The Gambia faced the question of how to obtain funds from villages to finance the cost of insecticide, but knew very little about current village fundraising for development purposes. A survey was conducted of such fundraising, and questions also asked about willingness to pay for insecticide and preferred means of paying. All 53 villages surveyed paid taxes/rates, but 34% of villages reported no voluntary fundraising. The most common reason for collecting money was for the maintenance of wells (40% of villages). Collective farming was used as a means of raising money in 32% of villages. There was some variation in the type and extent of fundraising by region and also by the predominant ethnic groups of the village. Villages with voluntary fundraising activities seemed to have well established collective mechanisms for agreeing on sums to be collected and their use, and for collecting and recording income and expenditure. Non-payment was rare, and misuse of funds was not reported. Respondents were asked how much compounds might be willing to pay for insecticide impregnantion: the most frequently cited maximum amounts were D5 and 10, and minimum D1 and 5 (D15 = 1 pound). The paper discusses payment options for insecticide, such as whether the village should be allowed to decide itself how to raise funds, and whether the payment should be made only by households with nets or by a village-wide mechanism such as collective farming.(ABSTRACT TRUNCATED AT 250 WORDS)

Agriculture↗

PubMed1977

The impact of contamination by organochlorine insecticides on poultry nutrition and feeding.

Nutrient interactions with organochlorine insecticides have been described primarily for vitamin A and protein. Storage of liver vitamin A is reduced by DDT and dieldrin. Low protein diets protect rats from heptachlor toxicity, whereas the toxicity of DDT, dieldrin and lindane is reduced by increasing the quantity and quality of diet protein intake. Biological performance of poultry is adversely affected by 50 to 500 ppm of most of these compounds. Hatchability of eggs and survival of chicks from hens fed insecticides are usually the most sensitive parameters of toxicity. Higher levels of DDT decrease thyroid activity. While several insecticides reduce egg shell thickness in wild birds, such changes are not observed in poultry. Extensive low level contamination of poultry tissues and eggs results from the organochlorine insecticides, with the exception of methoxychlor where tissue residues are not a problem. Tissue and egg accumulation of residues is related to dose but quantitatively different for each organochlorine compound. Tissue withdrawal and excretion takes place slowly and most of the compounds are metabolized by liver hydroxylating enzymes to various derivatives that are also stored in the body. In one case (heptachlor epoxide), the oxidation product is more toxic than the body. In one case (heptachlor epoxide), the oxidation product is more toxic than the parent compound.

Agriculture↗

PubMed1996

[Resistance of insects to insecticides. Molecular mechanisms and epidemiology].

The aim of this paper is to indicate the main strengths which are involved in the spread of insecticide resistance genes. These forces are more or less well known in population genetics, there are: mutations which are involved in the creation of new alleles well adapted to insecticides; migration which is responsible for the geographical extension of resistance and selection which screened among the various alleles those which are best adapted in the geographical and ecological context. The biological model described in this paper is the mosquito Culex pipiens which is the best known model at that time. Many works have been done on the resistance to insecticides in this species. On the other hand, the molecular mechanisms involved in insecticide resistance have been described from various invertebrates.

Animals↗