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PubMed1989

Polychlorinated convulsant insecticides potentiate the protective effect of NaCl against heat inactivation of [3H]flunitrazepam binding sites.

Six polychlorinated convulsant insecticides that potently inhibit t-[35S]butylbicyclophosphorothionate ([35S]TBPS) binding to rat brain membranes also potentiate the protective effect of NaCl (200 mM) against heat inactivation of [3H]flunitrazepam binding sites on the same membranes. Similar effects were obtained with all "cage" convulsants tested. The rank order of potencies as heat protection potentiators was similar to the rank order of potencies as inhibitors of [35S]TBPS binding (alpha-endosulfan greater than endrin greater than dieldrin greater than toxaphene greater than lindane). alpha-Endosulfan and endrin are more potent in both respects than any previously reported picrotoxin-like (cage) convulsant, but are much less toxic to mammals. The greatly reduced toxicities of alpha-endosulfan and endrin in mammals may reflect partial gamma-aminobutyric acid (GABA)-neutral properties of these compounds. Time courses of heat inactivation of [3H]flunitrazepam binding sites in the presence of 200 mM NaCl plus saturating concentrations of endrin or picrotoxin revealed monophasic components constituting about 88% of the binding sites, suggesting that virtually all [3H]flunitrazepam binding sites are coupled to picrotoxin binding sites in the GABA/benzodiazepine/picrotoxin receptor complex. Protection against heat inactivation constitutes a useful tool for characterizing the various allosterically linked binding sites in neurotransmitter receptor complexes.

Animals↗
PubMed1989

GABA receptors on the somatic muscle cells of the parasitic nematode, Ascaris suum: stereoselectivity indicates similarity to a GABAA-type agonist recognition site.

1. The gamma-aminobutyric acid (GABA) receptors on the somatic muscle cells of Ascaris, which mediate muscle cell hyperpolarization and relaxation, have been characterized by use of intracellular recording techniques. 2. These receptors are like mammalian GABAA-receptors in that the response is mediated by an increase conductance to chloride ions. The GABAA-mimetic, muscimol, has a relative potency of 0.40 +/- 0.02 (n = 3) compared to GABA. 3. The stereoselectivity of the GABA receptor on Ascaris is identical to that for the mammalian GABAA-receptor, as determined from the relative potency of three pairs of enantiomers of structural analogues of GABA. 4. The most potent agonist is (S)-(+)-dihydromuscimol which is 7.53 +/- 0.98 (n = 5) times more potent than GABA. 5. The Ascaris GABA receptor is not significantly blocked, at concentrations below 100 microM by the potent, competitive GABAA-receptor antagonist, SR95531. 6. The Ascaris GABA receptor does not recognise agents that are known to block the GABA gated chloride channel in mammalian preparations such as t-butylbicyclophosphorothionate (TBPS, 10 microM, n = 2) or the insecticide dieldrin (100 microM, n = 3). 7. GABAergic responses in Ascaris are not potentiated by pentobarbitone (100 microM, n = 3) or flurazepam (100 microM, n = 3). 8. The potencies of various GABA-mimetics in the Ascaris preparation have been compared with their potency at displacing GABAA-receptor binding in mammalian brain. Excluding the sulphonic acid derivatives of GABA, the correlation coefficient (r) between the potencies of compounds in the two systems is 0.74 (P less than 0.01). The significance of this correlation is discussed. 9. The pharmacology of the Ascaris GABA receptor is discussed in relation to other invertebrate systems and the mammalian subclassification of GABA receptors.

Animals↗
PubMed1978

Correlations between EEG and multiple unit activity of cortifugal axons at the onset of drug induced seizures in cats.

The onset of sustained multiple unit activity (MUA) in corticofugal axons was found to precede the onset of tonic EEG activity in 91 of 92 seizures produced by administering pentylenetetrazol, strychnine, or dieldrin to cats. Latency differences from 0-8 sec were observed with a mean of 3 sec. A trend was noted for shorter latencies with subsequent seizures in the same subject. No differences in latency were seen for spontaneous as compared to evoked seizures. Much variation was encountered in the pattern of MUA and EEG development at seizure onset. In general seizures with well-defined EEG components of desynchronization, tonic and clonic activity had the greatest latency differences and the least correspondence between MUA and EEG. Seizures with the abrupt emergence of tonic or clonic activity had the smallest latency differences and the best correspondence between MUA and EEG. Large changes in the activity along corticofugal axons were observed without EEG correlates. The evidence supports the concept that the degree of synchrony within the cortical (pyramidal) cell population is critical to the emergence and development of EEG during the tonic and clonic phases of a seizure. The data suggest that, in some cases, important changes in corticofugal output may contribute to and reinforce the activity in subcortical loci implicated in generalized seizure onset.

Action Potentials↗
PubMed1976

Insecticides in human breast milk.

Fifty samples of human breast milk were analysed by gas chromatography and thin layer chromatography for DDT (dichlordiphenyltrichloraethan), hexachlorobenzol, benezene-hexachlorides, dieldrin, aldrin and heptachlorepoxide. The three first substances were found in all samples in amounts varying from quite small up to eleven times the WHO recommended maximum for cow milk. The other substances were found in fewer milk samples, however, in some of these samples they were found in relatively high amounts. In Norway, only DDT has been investigated earlier (4), and compared to that study, there has been no significant change in the mean concentration of DDT in human breast milk during the last five years. The insecticide content was highest in colostrum and decreased with increasing duration of lactation. Considerable fluctuations in the content of insecticides were recorded in repeated milk samples collected from the same woman a few days apart. The percentage of samples with insecticide content higher than that permitted for cow's milk was greater in May/June (79%) than in early April (54%). The significance of these findings is discussed.

Aldrin↗
PubMed1981

WHO collaborative breast feeding study. I. Organochlorine contaminants in individual samples of Swedish human milk, 1978--1979.

Individual samples of human milk collected in Uppsala at 3 months post-partum (18 samples) or 6 months post-partum (23 samples) were analysed for chlorinated insecticides and polychlorinated biphenyls (PCBs) by gas chromatography. The mean levels of the organochlorine compounds in the 3- and 6-month groups were similar. The mean content of DDE, the major metabolite of DDT, in all the samples was 54 micrograms/kg fresh weight (1.3 mg/kg on a fat basis) with a range of 8.4--220 micrograms/kg (0.49--3.0 mg/kg fat). The results confirm that the decline since 1967 in the levels of DDT and its metabolites in Swedish human milk reported by other authors is continuing. The levels of dieldrin and beta-hexachlorocyclohexane found are lower than those reported earlier in Sweden, whereas the levels of hexachlorobenzene are about the same. On the other hand, the levels of PCBs (mean 64 micrograms/kg, range 15--150 micrograms/kg, fresh weight, equivalent to 1.6 mg/kg, range 0.84--2.9 mg/kg, on a fat basis) are higher than those reported earlier in Swedish human milk. Although the calculated intake of the DDT complex (DDT + DDE + DDD) by some of the suckling infants exceeds the acceptable daily intake proposed by a FAO/WHO expert group, it does not constitute a reason for recommending any restrictions on breast feeding--for nutritional, immunological and other reasons it should be encouraged.

Adult↗
PubMed1983

Organochlorine contaminants in Swedish human milk from the Stockholm region.

The levels of fat-soluble organochlorine contaminants in human milk in the Stockholm region are decreasing. For p,p'-DDT, p,p'-DDE, and dieldrin a reduction has taken place during the last decade, but the levels of polychlorinated biphenyls (PCBs) started declining only from about 1977. Generally, the pooled samples from the Mothers' Milk Centre in Stockholm in 1980 contained lower levels of organochlorine contaminants than the current Swedish maximum acceptable limits for milk. In 2% of the samples the total DDT levels slightly exceeded the limit of 0.05 mg DDT + DDD + DDE/kg. Milk from three mothers was analysed during the nursing of two or three consecutive infants. In each case, the levels of organochlorine contaminants declined.

Adult↗
PubMed1975

Ascorbic acid requirements and metabolism in relation to organochlorine pesticides.

Those organochlorine pesticides which possess both high lipoid solubility and high resistance to biodegradation are prone to accumulation in animal tissues and produce relatively long-term effects as toxicants. Such compounds, typified by DDT, Dieldrin, and Lindane, are profound inducers of hepatic microsomal enzymes, including parts of the glucuronic acid and ascorbic acid biosynthetic pathways. Consequently, administering such pesticides to rats in accompanied by enhanced formation and excretion of D-glucuronic acid and L-ascorbic acid, or D-glucaric acid in the case of guinea pigs. Secondarily, the efficiency in biodegrading the pesticides is reduced in ascorbic-acid-deficient guinea pigs with correspondingly greater residue accumulation in tissue. This would aggravate chronic toxic effects of the compounds. Finally, the capacity of the liver to adapt to the presence of such toxicants through enhanced microsomal enzymatic levels appears to be sensitive to its ascorbate status. Impaired enzyme induction is apparent quite early during ascorbic acid depletion in guinea pigs. The enhanced turnover of ascorbate produced by such pesticides, the poor enzymatic adaptation to them during ascorbate depletion and the dependency of the oxidase system upon adequate ascorbate, all point to the central significance of ascorbate status in the liver, and possibly other tissues, as a determinant of their chronic toxicity.

Animals↗
PubMed1981

A survey for resistance in cattle ticks to acaricides.

A survey was made from late 1976 to late 1977 to determine the extent of resistance to acaricides in the cattle tick Boophilus microplus in Queensland. Questionnaires and requests for samples of ticks were forwarded to more than 900 randomly selected stock owners in the tick infested area which had been divided into 4 regions. Far North, Coastal North, Coastal Cental and South East. The response measured by the number of tick samples tested was 43%. The prevalence of resistance to organophosphorus (OP) compounds was highest in South East where 96% of the farms had OP-resistant ticks and 95% had the Biarra strain and lowest in Far North where 12% of the farms had OP-resistant ticks and 10% had the Biarra strain which was the predominant one in all regions. The highest percentages of the Ridgelands strain (35%) and the Tully strain (30%) occurred in Coastal North. The South East had the highest percentage of Mt Alford (30%). Although chlorinated hydrocarbons were banned for use in control of ticks in 1962, 49% of the farms in South East had some ticks resistant to dieldrin but in Far North it was only 2%. DDT-resistant ticks, which because of cross resistance to synthetic pyrethroids will affect the future use of this group, were present on 8% of the farms in both Coastal North and Coastal Central and 3% in South East and Far North. No resistance to the amidines, chlordimeform, chloromethiuron or amitraz was found.

Animals↗
PubMed1990

Occurrence of organochlorine residues in Australian meat.

In spite of several quality control procedures used by Australia to ensure the wholesomeness of export meat, a number of pesticide residue violations were identified in the Australian product exported to the USA in May 1987. The pesticides involved were the organochlorines, dieldrin and heptachlor. The problems were caused by the persistence of organochlorines in soils and their illicit use or contamination of storage facilities. Animals grazing contaminated pasture, ingesting contaminated feed or held in contaminated yards over a period, bioaccumulated residues in their adipose tissues which eventually exceeded maximum residue limits (MRL) and caused violations. Though there was no immediate public health risk, the Australian Quarantine and Inspection Service (AQIS) of the Commonwealth Department of Primary Industries and Energy (DPIE), acted expeditiously to determine and eliminate the factors causing these problems, which threatened Australia's beef export industry worth in excess of two billion dollars annually. An overall strategic plan, "The Integrated Action Plan", was formulated and implemented by AQIS with the assistance of the relevant Departments of the States and the Northern Territory (NT), meat processing and export industries and livestock producer bodies. As a result of this action, the likely sources of contamination were identified and controlled. The National Residue Survey (NRS) was enhanced, a National Residue Data Base (NRDB) was established and a centralised computer system interactive with abattoirs, laboratories and animal health authorities developed. The cattle farm identity tail tag system already in place, capable of tracing cattle to the farm of origin was refined and trace back systems for sheep and pigs were utilised.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

A unique amino acid of the Drosophila GABA receptor with influence on drug sensitivity by two mechanisms.

1. The Drosophila gene Rdl (resistance to dieldrin) encodes a GABA receptor. An alanine-to-serine mutation in this gene at residue 302 confers resistance to cyclodiene insecticides and picrotoxin. Patch clamp analysis of GABA receptors in cultured neurons from wild type and mutant Drosophila was undertaken to investigate the biophysical basis of resistance. 2. In cultured neurons from both wild type and mutant strains, GABA activated a channel that reversed near 0 mV in symmetrical chloride. GABA dose-response characteristics of wild type and mutant receptors were very similar. 3. GABA responses in neurons from the mutant strains showed reduced sensitivity to the GABA antagonists picrotoxin, lindane and t-butyl-bicyclophosphorothionate. Resistance ratios were 116, 970 and 9 for the three blockers, respectively. Inhibition increased with blocker concentration in a manner consistent with saturation of a single binding site. 4. The mutation reduced the single channel conductance by 5% for inward current and 17% for outward current. The single channel current was approximately 60% lower for outward current than for inward current in both wild type and mutant. 5. Open and closed times were both well fitted by the sum of two exponentials. Resistance was associated with longer open times and shorter closed times, reflecting a net stabilization of the channel open state by a factor of approximately five. 6. The mutation was associated with a marked reduction in the rate of GABA-induced desensitization, and a net destabilization of the desensitized conformation by a factor of 29. 7. The Rdl mutation manifests resistance through two different mechanisms. (a) The mutation weakens drug binding to the antagonist-favoured (desensitized) conformation by a structural change at the drug binding site. (b) The mutation destabilizes the antagonist-favoured conformation in an allosteric sense. The global association of a single amino acid replacement with cyclodiene resistance suggests that the resistance phenotype depends on changes in both of these properties, and that insecticides have selected residue 302 of Rdl for replacement because of its unique ability to influence both of these functions. 8. The location of alanine 302 in the sequence of the Rdl gene product supports a mechanism of action in which convulsants such as picrotoxin bind within the channel lumen, where they induce a rapid conformational change to the desensitized state.

Alanine↗
PubMed1999

Endrin inhibits adipocyte differentiation by selectively altering expression pattern of CCAAT/enhancer binding protein-alpha in 3T3-L1 cells.

The effects of selected chlorinated cyclodiene pesticides on the adipocyte differentiation process were examined using the 3T3-L1 adipocyte model in vitro. Endrin was found to cause a dose-dependent inhibition of adipocyte differentiation in 3T3-L1 cells. Aldrin and dieldrin were less potent than endrin in interfering with the adipogenic process. Endrin's inhibitory effect was effective only when the pesticide was present in the medium during the first 48 h after exposure of 3T3-L1 cells to adipogenic inducers. Immunoblots analysis revealed that endrin caused a dose-dependent, selective inhibition of the intracellular levels of CCAAT enhancer binding protein (C/EBP)alpha without altering the expression patterns of C/EBPbeta or C/EBPdelta along the differentiation. Supershift analysis showed that DNA-binding capacity of C/EBPalpha was affected most by endrin treatment. Endrin also caused a decrease in the elevation of the adipogenic factor peroxisome proliferator-activated receptor (PPAR)gamma elicited by the adipogenic inducers. However, the cotreatment with troglitazone, a thiazolidinedione known to activate PPARgamma, did not suppress the antiadipogenic action of endrin, indicating that its direct action site is not PPARgamma receptor. Endrin also altered the pattern of activation of nuclear factor-kappaB, a factor activated by 12-O-tetradecanoylphorbol-13-acetate and tumor necrosis factor-alpha, which are known to interfere with adipocyte differentiation. Thus, endrin inhibited the normal decrease in nuclear factor-kappaB-DNA binding observed as cells are acquiring the adipocyte phenotype at a late stage of differentiation. Our results suggest that endrin inhibits adipocyte differentiation through the specific suppression of C/EBPalpha.

3T3 Cells↗
PubMed1976

Epoxide to olefin: a novel biotransformation in the rumen.

Studies with an insect juvenile hormone mimic and the insecticide dieldrin have shown that enzymatic processes in the rumen reduce the epoxide moiety in these compounds to an olefin. This reaction is apparently microbial in origin and does not involve an observable intermediate. Epoxide reductions in the digestive tract of ruminants and possibly other mammals may be important in the detoxication of biologically active epoxides, including pesticides, alkylating agents, and carcinogens.

Animals↗
PubMed1967

Dietary intake of pesticide chemicals. Calculated daily consumption of pesticides with foods are discussed and compared with currently accepted values.

Residues of chlorinated organic pesticide chemicals were commonly found in all diet samples and all food classes within samples except beverages at a daily intake of 0.0014 mg per kilogram of body weight. Meat, fish, and poultry were the major source of pesticide residues and, when combined with dairy products, account for more than half of the intake of chlorinated organic pesticide chemicals. Fruits, garden fruits, and grain foods each accounted for about 10 percent of the intake of chlorinated pesticides. The DDT, its two analogs, dieldrin, lindane, and heptachlor epoxide account for 85 percent of the total intake of chlorinated pesticides. A single pesticide, DDT, accounts for one-third of the total. There was no statistically significant change in frequency or quantities of these compounds during this study. Frequency and quantities of the 14 additional chlorinated pesticides were too low to be meaningful.

Animals↗
PubMed1969

Insect metabolism of photoaldrin and photodieldrin.

Photoaldrin and photodieldrin, sunlight products of adrin and dieldrin, are rapidly metabolized to a more toxic material by flies and mosquito larvae. It is suggested that this conversion is the cause for the enhanced toxicities of the photoproducts.

Aedes↗
PubMed1970

Marine phytoplankton vary in their response to chlorinated hydrocarbons.

Photosynthesis and growth in cultures of four marine phytoplankton species, isolated from different oceanic environments, were affected by three chlorinated hydrocarbons (DDT, dieldrin, and endrin) to varying extents. This ranged from complete insensitivity in Dunaliella to toxicity at concentrations of 0.1 to 1.0 part per billion of the pesticides in Cyclotella. Other forms were intermediate in their response.

Bridged-Ring Compounds↗
PubMed1970

Antagonism by DDT of the effect of valinomycin on a synthetic membrane.

The potassium conductance which is induced by 10(-6) molar valinomycin in a lecithin-decane membrane is reversed by 3 x 10(-6) molar DDT. Membranes not treated with valinomycin are not affected by DDT. This blockade of potassium conductance parallels the effect of DDT on axonic conduction. Dieldrin and lindane, whose physiological actions are in some ways like those of DDT, do not affect valinomycin-induced conductance of lecithin-decane membranes.

Alkanes↗
PubMed1996

Synergistic activation of estrogen receptor with combinations of environmental chemicals.

Certain chemicals in the environment are estrogenic. The low potencies of these compounds, when studied singly, suggest that they may have little effect on biological systems. The estrogenic potencies of combinations of such chemicals were screened in a simple yeast estrogen system (YES) containing human estrogen receptor (hER). Combinations of two weak environmental estrogens, such as dieldrin, endosulfan, or toxaphene, were 1000 times as potent in hER-mediated transactivation as any chemical alone. Hydroxylated polychlorinated biphenyls shown previously to synergistically alter sexual development in turtles also synergized in the YES. The synergistic interaction of chemical mixtures with the estrogen receptor may have profound environmental implications. These results may represent a previously uncharacterized level of regulation of estrogen-associated responses.

Binding, Competitive↗