Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Methoxychlor”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18Linked to original sources
PubMed1959

Cross-resistance in insecticide-resistant strains of the German cockroach. Blattella germanica (L.

The authors describe a series of experiments designed to determine the extent to which cross-resistance exists in insecticide-resistant strains of the German cockroach. The tests were conducted by exposing females from a DDT-resistant strain, a chlordane-resistant strain, and a non-resistant strain to varying concentrations of several insecticides. From these tests mortality data were obtained and are presented in the form of regression lines.The insecticides used were DDT, methoxychlor, chlordane, dieldrin, Prolan, malathion, allethrin, and Lethane; these were chosen so that a wide variety of chemical types would be represented.The results indicate that the DDT-resistant strain is highly resistant to DDT and to its analogue, methoxychlor, but not to any of the other insecticides tested. Similarly, the chlordane-resistant strain is highly resistant to chlordane and to its analogue, dieldrin, but is susceptible to the other toxicants listed.From these results, as well as those obtained by others, it appears that the picture of cross-resistance in the German cockroach is in essential agreement with that which is emerging for other insects throughout the world.

Animals↗
PubMed1970

Effects of temperature on the irritability caused by DDT and DDT-analogues in anopheline mosquitos.

The author reports a series of investigations into the effects of temperature on irritability, caused by DDT or its analogues methoxychlor and DDD, in Anopheles labranchiae atroparvus and An. gambiae, species B; into the irritability of three other anophelines upon exposure to deposits of water-dispersible DDT powder; and into the relation between aging and DDT-irritation in anophelines. Irritability was measured by both the number of take-offs and the duration of flight over a 20-minute period at temperatures of from 19 degrees C to 32 degrees C.The flight activity of An. 1. atroparvus and An. gambiae B increased with increasing temperature to a peak at 23 degrees C for the former and 27 degrees C for the latter; it then fell with further increase in temperature to 32 degrees C.Over 20 minutes, the DDT-resistant An. pharoensis was less irritated than either An. gambiae A or An. punctulatus farauti (both susceptible) but over 30 minutes was more so than An. p. farauti.Among other findings were that methoxychlor and DDD were stronger irritants than DDT and that irritability declined with increasing age of the mosquitos.

Age Factors↗
PubMed2003

Estrogenic endocrine disruptive components interfere with calcium handling and differentiation of human trophoblast cells.

During development, calcium (Ca) is actively transported by placental trophoblasts to meet fetal nutritional and the skeletal mineralization needs. Maternal exposure to estrogenic pesticides, such as 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (DDT) and methoxychlor (MTC), has been shown to result in reproductive disorders and/or abnormal fetal development. In this study, we have examined the effects of exposure of trophoblastic cells to MTC and DTT, in comparison to 17beta-estradiol (E2) and diethylstilbestrol (DES), to test the hypothesis that cellular Ca handling is a target for these endocrine disruptive components. Treatment with DDT, MTC, DES, or E2 increased cellular Ca uptake, and the expression of trophoblast-specific human Ca binding protein (HCaBP) was down-regulated by both MTC and DDT. Treatment with MTC, DDT, and DES inhibited cell proliferation, induced apoptosis, and suppressed expression of several trophoblast differentiation marker genes. These effects were reversed by overexpression of metallothionein IIa, a gene highly responsive to cadmium and other metals. These results strongly suggest that trophoblast Ca handling functions are endocrinally modulated, and that their alteration by candidate endocrine disruptors, such as MTC and DDT, constitutes a possible pathway of the harmful effects of these components on fetal development.

Adenosine Triphosphatases↗
PubMed1993

Effects of added albumin on the kinetic isotope effect observed in the microsomal oxidative demethylation of the methoxyl group.

The kinetic deuterium isotope effect on the microsomal oxidative demethylation of methoxyl groups was measured using methoxychlor, an insecticide, as a model compound. When the metabolic reactions were conducted in the presence of bovine serum albumin, the observed isotope effect was smaller than that in its absence. The values were unaltered when the albumin concentration was changed from 1% to 2%. The results were interpreted by the alteration of the ES-complex formation/dissociation rate with the interaction between substrate and albumin.

Animals↗
PubMed2001

An in vitro reporter gene assay method incorporating metabolic activation with human and rat S9 or liver microsomes.

A metabolic activation system with an S9 fraction or liver microsomes was applied to a reporter gene assay in vitro for the screening of estrogenicity of chemicals. The endpoint (luciferase) was luciferase induction in cells transfected with a reporter plasmid containing an estrogen-responsive element linked to the luciferase gene. Compounds were applied to the reporter gene assay system after pretreatment or simultaneous treatment with an S9 fraction or liver microsomes. Both trans-stilbene and methoxychlor themselves showed no or little estrogenicity, but when they were treated with an S9 fraction or liver microsomes, they demonstrated strong effects, indicating their metabolites to be estrogenic. When four pyrethroid insecticides were subjected to this assay system, however, they showed no estrogenicity even with liver microsome or S9 mix treatment.

Animals↗
PubMed2002

Oral estrogen masculinizes female zebra finch song system.

It is well established that parenteral treatment of female zebra finch chicks with estradiol masculinizes their song control nuclei and that as adults they are capable of song. Concern over the widespread use of putative environmental estrogens caused us to ask whether oral exposure to estrogens (a natural route of exposure) could produce similar effects. We dosed chicks orally with estradiol benzoate (EB; 1, 10, 100, and 1000 nmol/g of body mass per day, days 5-11 posthatch), the non-ionic surfactant octylphenol (100 and 1000 nmol/g), or the pesticides methoxychlor (100 and 1000 nmol/g) and dicofol (100 nmol/g) and measured their song control nuclei as adults. EB treatment produced increases in song nuclei comparable to that induced by parenteral administration of estrogens. This is the first study of which we are aware to use an oral route of administration, which simulates the natural process of parent birds feeding their nestlings. We conclude that oral exposure to estradiol alters song control nuclei and we report in a related paper (Millam et al., 2001) that such exposure severely disrupts reproductive performance. Although we detected no influence of xenobiotics on induction of song control nuclei the possibility remains that oral exposure to xenoestrogens in high enough doses could affect development.

Animals↗
PubMed1997

Evaluation of chemicals with endocrine modulating activity in a yeast-based steroid hormone receptor gene transcription assay.

There is a concern that chemicals in our environment are affecting human health by disrupting normal endocrine function. Much of the concern has focused on chemicals that can interact directly with steroid hormone receptors. We have used a yeast-based assay to assess chemical interactions with the estrogen, androgen, and progesterone receptors. The yeast transformants used in this study contained the human estrogen, androgen, or progesterone receptor along with the appropriate steroid responsive elements upstream of the beta-galactosidase reporter gene. Chemicals were added to yeast cultures in doses ranging from 10(-12) to 10(-4) M and following incubation, the yeasts were then lysed and assayed for beta-galactosidase activity. Diethylstilbesterol and 17-beta estradiol were most active in the estrogen receptor assay, followed by the phytoestrogen, coumestrol. p-Nonylphenol and bisphenol A were approximately 5000- and 15,000-fold less active, respectively, than estradiol. Methoxychlor, DDT and its metabolites, o,p'-DDD, and o,p'-DDE ranged in potency from 5 to 24 X 10(6) less potent than estradiol. Testosterone and dihydrotestosterone were most potent in the androgen receptor assay, followed by estradiol and progesterone. p,p'-DDE was approximately 10(6)-fold less potent than testosterone. None of the industrial chemicals tested interacted with the progesterone receptor. These data demonstrate the utility of using yeast-based receptor assays for detecting chemical interaction with steroid receptors and these assays should serve as a useful component of an in vitro-in vivo strategy to assess the effects of chemicals on endocrine function.

DDT↗
PubMed2003

Alteration of pituitary hormone-immunoreactive cell populations in rat offspring after maternal dietary exposure to endocrine-active chemicals.

We previously performed dose-response studies of genistein, diisononyl phthalate, 4-nonylphenol, methoxychlor (MXC), and bisphenol A to examine the impact of maternal dietary exposure from gestational day 15 to postnatal day 10 on the development of rat reproductive system in later life. Among the chemicals MXC alone showed typical estrogenic effects only at the maternally toxic 1200 ppm. The present study was performed to examine the sensitivity of immunohistochemical analysis of pituitary cells of offspring similarly exposed to each chemical for detection of endocrine-disrupting effects. For this purpose, ratios of pituitary cells expressing luteinizing hormone (LH), follicle stimulating hormone (FSH) and prolactin (PRL), were measured at 3 and 11 weeks of age. Ethinylestradiol (EE) at 0.5 ppm was used as a reference chemical. At week 3, decrease in the relative proportions of LH, FSH, and PRL cells in males and LH cells in females was evident with MXC at 1200 ppm. At week 11, increase was found for PRL cells from 240 ppm MXC, and FSH cells at 1200 ppm in females. On the other hand, EE increased the PRL cell percentage in females at week 3 but no effects were apparent at week 11. The other chemicals were without influence at either time point. The results suggest that the assessment of the pituitary cell populations might be a more sensitive approach to detect perinatal endocrine-disrupting effects than other methods. The difference in the pituitary effect between MXC and EE is discussed.

Administration, Oral↗
PubMed1985

The use of the bivalve Mytilus edulis as a test organism for bioconcentration studies. I. Designing a continuous-flow system and its application to some organochlorine compounds.

Most bioconcentration studies have previously been carried out using fish as a test organism. Equally important is the use of bivalves for this purpose, from both an ecological and an economic point of view. A continuous-flow system has thus been designed for use also with extremely hydrophobic substances and evaluated using 2,4',5-trichlorobiphenyl, methoxychlor, pentachlorobenzene, and lindane. The variation of the uptake in the individuals after 3 weeks' exposure was quite small (relative standard errors varied from 10.1 to 15.3% depending on the test substance), indicating a high degree of reproducibility. The bivalves, however, are known to close their valves under unfavorable conditions, which occasionally may bias the results. To overcome this disadvantage, it is suggested that an internal standard--i.e., a chemically defined compound--be added to the water simultaneously with the test substances. Although there is a principal risk for interactive effects, unexpected variations in the uptake can thus be compensated for by relating the concentration of the test substance to the concentration of the internal standard in the organisms. Comparisons between continuous-flow systems and static systems have also been made. It is concluded that continuous-flow systems are more suitable for studying hydrophobic compounds than static systems.

Animals↗
PubMed1987

A shake-flask test for estimation of biodegradability of toxic organic substances in the aquatic environment.

Disadvantages of current biodegradation tests are examined: the need for high substrate concentrations, lack of parent compound concentration measurements, no estimation of sediment effects, failure to indicate compounds to which microbial populations must adapt to degrade, and lack of site specificity in innocula selection. A modified river die-away test is proposed for determining biodegradability of organic compounds and testing for toxic degradation products. The present test uses shake flasks containing sterile (2% formalin) and nonsterile site water: both with, and without, site sediment (500 mg/liter). Concurrent toxicity testing with mysids or daphnids provides a sensitive assay for the detection of toxic metabolites. Examples of three test compounds are given: methyl parathion, which undergoes rapid, sediment-mediated biodegradation; dibutylphthalate, to which some microbial communities exhibit an adaptation phenomenon; and methoxychlor, which has a relatively low water solubility and high sediment partition coefficient. The relative merits of this test procedure are discussed.

Animals↗
PubMedDate not supplied

Influence of organochlorine pesticides on development of mouse embryos in vitro.

The effect of DDT, methoxychlor (MXC), and gamma-hexachlorocyclohexane (gamma HCH) on preimplantation mouse embryos in culture was evaluated by the proportion of eight-cell stage embryos developing to expanded and hatched blastocysts. A concentration of 29 micrograms/mL DDT or gamma HCH led to a complete degeneration of exposed embryos. The addition of 29 micrograms/mL MXC showed blastocyst formation (72.3%), but fewer than half of the blastocysts were intact and only 4.3% hatched from the zona pellucida. A concentration of 14.5 micrograms/mL DDT led to 57.5% blastocyst formation and to 6.8% hatched blastocysts; the same concentration of gamma HCH and MXC showed 66.7 and 95.9% blastocyst formation and 22.9 and 49% hatched blastocysts, respectively. The addition of 7.25 micrograms/mL led to 85.9% (DDT), 77.6% (gamma HCH), and 81% (MXC) blastocysts in total, and to 28.2, 35.5, and 49.4% hatched blastocysts, respectively. Compared with untreated controls, only the 3.625 micrograms/mL concentration for all pesticides showed no significant differences in blastocyst formation and hatching. These results show different toxicity of these three pesticides for the preimplantation mouse embryo in the order MXC < gamma HCH < or = DDT).

Animals↗
PubMed2004

Effects of environmental and natural estrogens on vitellogenin production in hepatocytes of the brown frog (Rana temporaria).

The objective of this study was to investigate the ability of the natural estrogens and synthetic estrogens as well as the estrogen mimics to induce estrogen-receptor mediated vitellogenesis in primary hepatocytes of the brown frog (Rana temporaria). Based on EC50 values the following order was determined for the potency of the estrogens: 17beta-estradiol (EC50: 19-43 nM) approximately ethynylestradiol (EC50: 13-80 nM)>estrone (EC50: 218-241 nM)>DES (EC50: 338-3537 nM). Exposure to bisphenol A and methoxychlor concentrations up to 100 microM did not have any effect on in vitro vitellogenesis.

Animals↗
PubMed2005

Effects of selected xenoestrogens on liver peroxisomes, vitellogenin levels and spermatogenic cell proliferation in male zebrafish.

Environmental estrogenic compounds or xenoestrogens can mimic natural estrogens and cause a variety of adverse effects on aquatic wildlife. The purpose of the present work was to investigate if xenoestrogens are able to cause proliferation of liver peroxisomes using zebrafish (Danio rerio) as a model. Adult male zebrafish were exposed for 15 days to 17beta-estradiol (E2) and the xenoestrogens dibutylphthalate (DBP), methoxychlor (MXC), 4-tert-octylphenol (OP) and 17alpha-ethynylestradiol (EE2). All five tested compounds caused significant proliferation of liver peroxisomes (p < 0.05) as indicated by increased peroxisomal surface and numerical densities and elevated activities of the peroxisomal beta-oxidation enzyme acyl-CoA oxidase (AOX). In the case of DBP, MXC and E2, positive significant correlations between peroxisomal density parameters and AOX were found. The treatments did not produce gross alterations in testis histology, but spermatogenic cell proliferation was disturbed in E2 and EE2-treated groups and vitellogenin levels increased significantly in fish exposed to MXC, OP, EE2 and E2 with respect to controls. Furthermore, a significant correlation between vitellogenin levels and AOX activity was found for MXC, OP and EE2 treatments, suggesting that for the latter xenoestrogens early estrogenic effects are associated with liver peroxisome proliferation. No such association occurred with typical peroxisome proliferators such as DBP.

Acyl-CoA Oxidase↗
PubMed2006

Organochlorine contaminants in complete clutches of Morelet's crocodile (Crocodylus moreletii) eggs from Belize.

Seven complete clutches of Morelet's crocodile (Crocodylus moreletii) eggs were collected in northern Belize and examined for organochlorine (OC) pesticide residues. The primary OC detected, p,p-DDE, was found in every egg analyzed (n=175). Other OCs detected included p,p-DDT, p,p-DDD, methoxychlor, aldrin, and endosulfan I. Concentrations of individual OCs ranged from 4 ppb (ng chemical/g egg wet weight) to greater than 500 ppb. A statistical evaluation of p,p-DDE levels in three complete clutches was used to derive the minimum number of eggs needed from a clutch to precisely determine the mean p,p-DDE concentration representative of that clutch. Sample sizes of 8 (80% confidence level) and 11 (90% confidence level) were determined to yield an accurate estimate of contaminant levels in a full clutch of eggs. The statistically recommended sample size of 11 eggs (at 90% confidence level) was successfully tested on the four additional clutches.

Aldrin↗
PubMedDate not supplied

Endocrine disruption and cognitive function in adolescent female rhesus monkeys.

Female rhesus monkeys (n=8/group) received daily oral doses of exogenous estrogen [diethylstilbestrol (DES), 0.5 mg/kg, methoxychlor (MXC), 25 or 50 mg/kg] for 6 months before and after the anticipated age of menarche. Behavior was assessed during and for 9 months after dosing. Visual discrimination performance (simultaneous nonmatch-to-sample with trial-unique stimuli) conducted during dosing demonstrated delayed improvement and poorer performance in the MXC50 group, with some similar effects in the DES group. Visual recognition memory, assessed with delays of < or = 3 s, was not apparently affected. Spatial working memory, assessed after dosing, also showed acquisition deficits and possible working memory difficulties in the MXC50 group. Spontaneous motor activity, monitored at 6-month intervals, was not affected by treatment. Late peak latencies of the auditory brainstem response (ABR) were shorter in the DES group 6 months after treatment, suggesting long-term effects on brain. The study suggests that some aspects of brain function can be modified by exposure to exogenous estrogen during pubertal development. Although DES is a more potent estrogen, the high-dose MXC group was more affected behaviorally. Differential effects of the two agents at the estrogen receptor subtypes (ER alpha and ER beta) may be relevant to the differential behavioral outcomes.

Animals↗
PubMed2005

Perinatal exposure to endocrine disrupting compounds alters behavior and brain in the female pine vole.

Endocrine-disrupting chemicals (EDCs) are synthetic chemicals that arise from sources such as pesticides and have the ability to mimic or inhibit gonadal steroid hormones. The objective of this research was to examine the effects of EDCs on the behaviors associated with monogamy and the expression of related neuropeptide receptors. Pine voles, a novel experimental mammal, were chosen because they display strong monogamous pair bonding. Female pine voles were orally administered estrogenic diethylstilbestrol (DES) and methoxychlor (MXC) or oil control throughout gestation and lactation of pups. Exposed pups were tested as adults. Preference for the mate and maternal behaviors were assessed. While the ability to form partner preferences was intact, DES-exposed females showed increased aggression toward a stranger, while MXC exposed females showed a strong trend toward spending more time alone. Oxytocin (OT) receptor binding in the brain was assessed for possible effects on this behaviorally important neuropeptide signaling system. The cingulate cortex showed a reduction in OT binding in the MXC group. These findings demonstrate that exposure to EDCs during pre- and neonatal development can alter female adult neural phenotype and behavior related to monogamous behavior traits.

Aggression↗
PubMed2005

Impact of maternal dietary exposure to endocrine-acting chemicals on progesterone receptor expression in microdissected hypothalamic medial preoptic areas of rat offspring.

We have previously examined the impact of perinatal exposure to ethinylestradiol (EE), methoxychlor (MXC), diisononyl phthalate (DINP), and genistein (GEN) in maternal diet on rat offspring, and found developmental and/or reproductive toxicity with 0.5 ppm EE, 1200 ppm MXC, and 20,000 ppm DINP. Although the toxicological profile with MXC was similar to the EE case, the population changes in pituitary hormone-producing cells totally differed between the two cases, changes being evident from 240 ppm with MXC. In the present study, to assess the impact of these agents on brain sexual differentiation, region-specific mRNA expression of estrogen receptors (ER) alpha and beta, the progesterone receptor (PR), gonadotrophin-releasing hormone, steroid receptor coactivators (SRC)-1 and -2, and calbindin-D in microdissected hypothalamic medial preoptic areas (MPOAs) at postnatal day 10 was first analyzed in rats exposed to 0.5 ppm-EE from gestational day 15 by real-time RT-PCR. Sexually dimorphic expression of ER alpha and PR was noted with predominance in females and males, respectively, EE up-regulating SRC-1 in males and ER beta and PR in females. Next, we similarly examined expression changes of ER alpha and beta, PR, and SRC-1 in animals exposed to MXC at 24, 240, and 1200 ppm, DINP at 4000 and 20,000 ppm, and GEN at 1000 ppm. MXC at 1200 ppm down- and up-regulated PR in males and females, respectively, and DINP at 20,000 ppm down-regulated PR in females, while GEN did not exert any clear effects. The results thus suggest that agents causing developmental and/or reproductive abnormalities in later life may affect hypothalamic PR expression during the exposure period in early life.

Animals↗
PubMed2002

Improvement of a two-stage carcinogenesis model to detect modifying effects of endocrine disrupting chemicals on thyroid carcinogenesis in rats.

In order to improve the sensitivity of our previously established thyroid carcinogenesis model and to clarify whether endocrine disrupting chemicals with weak estrogenic activity have any modifying effects on the development of thyroid proliferative lesions, 6-week-old female castrated F344 rats were first given a single subcutaneous injection of 2000 mg/kg body weight of N-bis(2-hydroxypropyl)nitrosamine. From 1 week later, they received diets with: no supplement (basal diet (BD) group); cholesterol pellets containing 0.5 mg 17 beta-estradiol 3-benzoate (EB); or diet admixed with 1000 ppm methoxychlor (MXC) or 10,000 ppm bisphenol A (BPA) for 20 weeks. Furthermore, additional groups were administered 200 ppm sulfadimethoxine (SDM) in the drinking water simultaneously with the BD, EB, MXC or BPA treatments. Thyroid follicular cell hyperplasias, adenomas and/or carcinomas were induced only in the EB+SDM group, the incidences of non-malignant lesions being significantly increased, as compared with the BD+SDM group values. Furthermore, the serum level of thyroid stimulating hormone (TSH) was significantly increased in this group. No significant variation in quantitative values for thyroid proliferative lesions or TSH levels were observed in the other treated groups. The results of the present study convincingly indicate that EB, with strong estrogenic activity, but not MXC and BPA, with weak estrogenic activities, exerts promoting effects on thyroid carcinogenesis in rats. The present modified rat two-stage thyroid carcinogenesis model appears to have advantages over our previous model for screening purposes.

Adenoma↗