Showing papers in "Drug and Chemical Toxicology in 1998"
TL;DR: This study demonstrates that the liver slice model is a simple and useful technique to investigate the underlying mechanisms of paracetamol-induced cell injury.
Abstract: The flux in rat hepatic ratio of adenosine triphosphate levels to adenosine diphosphate levels (ATP/ADP) during the onset and progression of paracetamol-induced cell injury both in vivo and in vitro were investigated and compared. Leakage of lactate dehydrogenase (LDH) and potassium (K+), and mg water/mg dry weight quantified cell injury. ATP and ADP levels were determined using the luciferin-luciferase bioluminescence assay. For in vitro studies, liver slices obtained from phenobarbitone-induced rats were exposed to 10 mM paracetamol for 120 min (T0-T120) and, then incubated without paracetamol up to a further 240 min (T120-T360). For in vivo studies, groups of four phenobarbitone-induced rats received i.p. injections of 800 mg/kg paracetamol. ATP/ADP ratios fall upon exposure to paracetamol both in vitro and in vivo. However, unlike the in vitro situation where the fall in ATP/ADP ratios precedes and accompanies the progression of cell injury, the in vivo fall in ATP/ADP ratios is shown to occur as cell injury measurements begin to recover to control levels. However, despite these differences classic paracetamol-induced centrilobular necrosis is observed to occur both in vitro and in vivo. This study demonstrates that the liver slice model is a simple and useful technique to investigate the underlying mechanisms of paracetamol-induced cell injury.
66 citations
TL;DR: In this paper, the toxicokinetics of sulfur mustard and its major DNA-adduct were studied in male hairless guinea pigs for the intravenous, respiratory and percutaneous routes.
Abstract: In order to provide a quantitative basis for pretreatment and therapy of intoxications with sulfur mustard (SM) the toxicokinetics of this agent as well as its major DNA-adduct were studied in male hairless guinea pigs for the intravenous, respiratory and percutaneous routes. the study comprised measurement of the concentration-time course of SM in blood and measurement of the concentrations of intact SM and its adduct to guanine in various tissues at several time points after administration of, or exposure to SM. SM was analyzed in blood and tissues by gas chromatography with automated thermodesorption injection and mass-spectrometric detection. DNA-adducts were measured via an immuno-slot-blot method.In contrast with nerve agents of the phosphofluoridate type, SM partitions strongly to various organs, especially the lung, spleen, liver and bone marrow. the respiratory toxicity of SM appears to be local, rather than systemic. Surprisingly, the maximum concentration of SM in blood upon percutaneous exposu...
54 citations
TL;DR: A careful comparison of protein and energy restriction revealed a greater degree of oxidative-stress of INH-RMP in protein-restriction.
Abstract: The role of protein and energy malnutrition in the pathogenesis of isoniazid (INH)-rifampicin (RMP) induced hepatic injury was investigated. Status of oxidative/antioxidative profile was the mechanistic approach to enumerate the nature of injury. Weanling rats were fed with ad-libitum quantity of isocaloric diets containing 5% casein based proteins for the production protein and energy malnutrition. INH and RMP (50 mg/kg of each) were injected intraperitonially for a period of two weeks. Analysis of serum transaminases and histopathological observations revealed hepatic injury. Hepatic thiols and blood glutathione were decreased significantly in INH and RMP treated groups. Among antioxidative enzymes, hepatic superoxide dismutase, catalase, glutathione peroxidase and glutathione-S-transferases (against CDNB and DCNB substrates) showed significant decline of activities in INH and RMP treated groups. the activities of hepatic glutathione reductase, glutathione-S-transferase (against EA substrate) an...
47 citations
TL;DR: Results indicated that bioactivated toxicants may be prone to greater variability in response amongst laboratories than compounds, which are detoxified, and warrant the continued use and further refinement of FETAX for alternative developmental toxicity assessment.
Abstract: Interlaboratory validation of an exogenous metabolic activation system (MAS) developed for the alternative, short-term developmental toxicity bioassay, Frog Embryo Teratogenesis Assay - Xenopus (FETAX) was performed with cyclophosphamide and caffeine. Seven study groups within six separate laboratories participated in the study in which three definitive concentration-response experiments were performed with and without the MAS in a side-by-side format for each chemical. Since both chemicals had been previously tested in FETAX, the test concentrations were provided to each laboratory prior to testing. Interlaboratory coefficient of variation (CV) values for unactivated cyclophosphamide (no MAS) were 15%, 15%, 29%, and 25% for the 96-hr LC50, 96-hr EC50 (malformation). Minimum Concentration to Inhibit Growth (MCIG), and Teratogenic Index (TI) values, respectively. Addition of the MAS increased the CV values of each endpoint at least 3.9-fold. Interlaboratory CV values for unactivated caffeine were 3...
43 citations
TL;DR: The developmental toxicity ofSteviol, a metabolite of stevioside, was studied in hamsters and one craniomeningocele was found in a fetus under the maternal toxic condition in steviol-treated at a dose of 0.75 g/kg BW/day.
Abstract: The developmental toxicity of steviol, a metabolite of stevioside, was studied in hamsters. Pregnant hamsters were intubated with steviol at dose levels of 0, 0.25, 0.5, 0.75 and 1.0 g/kg BW/day on days 6-10 of gestation. Steviol at doses of 0.75 and 1.0 g/kg BW/day were highly toxic to both dams and fetuses. Significant decrease of maternal body-weight gain during the experimental period (days 6-14) and high percentage of maternal mortality indicated the general toxicity of these two high doses. The number of live fetuses per litter and mean fetal weight also significantly decreased in the steviol-treated animals at doses of 0.75 and 1.0 g/kg BW day. The animals treated with an intermediate dose (0.50 g/kg BW/day) exhibited less signs of maternal and developmental toxicity than the two high doses (0.75 and 1.0 g/kg BW/day). One craniomeningocele was found in a fetus under the maternal toxic condition in steviol-treated at a dose of 0.75 g/kg BW/day. Neither the skeleton nor visceral development of the offspring was affected by steviol treatment except delayed ossification of the xiphoid (bifid) and long bones of the limbs and supernumerary thoracic ribs (14th ribs) tended to be increased at doses of 0.5 to 1.0 g/kg BW/day steviol. No dose-related teratogenesis was detected. From the result of the present study concerning maternal toxic condition and embryotoxicity, an oral dose of 0.25 g steviol/kg BW/day is regarded as having no observable effect. This steviol-treated dose is derived from stevioside 625 mg/kg BW/day which is approximately 80 times higher than the suggested acceptable daily intake of stevioside for humans (7.938 mg/kg BW/day).
36 citations
TL;DR: In this article, it was shown that intramuscular administration of the adenosine receptor agonists NECA (5'-N-E-carboxamido-adenosine) or CPA (N6-cyclopentyl adenoine) 1 min following a subcutaneous soman poisoning (1.5-2LD50) in rats, resulted in an improvement of survival rate (24 h), as opposed to high levels of extracellular brain ACh in untreated animals.
Abstract: Current treatment of acute organophosphate (OP) poisoning includes a combined administration of a cholinesterase reactivator (oxime), a muscarinic receptor antagonist (atropine) and an anticonvulsant (diazepam). This treatment is not adequate since it does not prevent neuronal brain damage and incapacitation. Here, as in a recent review it is stated that other therapeutic approaches may improve protection. Former studies on the 'direct effects' of oximes led to the conclusion that drug-induced inhibition of acetylcholine (ACh)-release shortly (1 min) after the acute OP-intoxication, could prevent and counteract convulsions and improve survival. In general, the accumulation of ACh in the synaptic cleft is considered to be responsible for the symptoms that ultimately lead to death. Therefore, prevention or suppression of this excessive accumulation of ACh could be a generic approach to antagonize OP-poisoning. Preliminary evidence for this concept has been put forward. Evaluation of drugs that would be able to prevent and counteract ACh accumulation, led to the conclusion that adenosine receptor agonists could be promising candidates. Pilot experiments demonstrated that intramuscular administration of the adenosine receptor agonists NECA (5'-N- ethylcarboxamido-adenosine) or CPA (N6-cyclopentyl adenosine) 1 min following a subcutaneous soman poisoning (1.5-2LD50) in rats, resulted in (1) prevention or postponement of chewing, salivation, convulsive activity, and respiratory distress (cholinergic symptoms), (2) improvement of survival rate (24 h), (3) a low level of extracellular brain ACh, as opposed to high levels of extracellular brain ACh in untreated animals. It is concluded that (1) adenosine agonists protect acutely soman-poisoned rats without the need of additional treatment with atropine, oxime or diazepam, (2) prevention of ACh accumulation in this way may be a new generic approach in the treatment of OP-poisoning.
35 citations
TL;DR: The study suggests that low dose chronic exposure of lindane causes neurobehavioral, neurochemical, and electrophysiological effects involving GABA-ergic mechanism(s).
Abstract: Lindane is widely used as an insecticide and scabicide in mammals. High doses in chronic exposures caused hyperexcitability and convulsions and impaired motor activity involving GABA-ergic mechanism. To investigate the role of GABA/Benzodiazepine mechanism in the neurotoxicity of low doses of lindane, rats were administered 2, 3, or 5 mg/kg orally for 90 days and behavioural, electrophysiological, and neurochemical studies were conducted. The animals exposed to lindane exhibited increased geotaxis and decreased spontaneous drug-induced locomotor activity (which further potentiated by phenobarbitone and increased after leptazol). The EEG of the treated rats showed high voltage slow-wave activity (HVSA) patterns with occasional spindles (9-10 HZ-amplitude of 100 uv). A significant increase (p < 0.01) in GABA levels in cerebellum and significant increase in benzodiazepine receptors in cerebellar membrane measured by (3H)flunitrazepam binding were observed in the animals exposed to 3 and 5 mg lindane. The study suggests that low dose chronic exposure of lindane causes neurobehavioral, neurochemical, and electrophysiological effects involving GABA-ergic mechanism(s).
34 citations
TL;DR: The results indicate the need to further investigate the relationship of increased caloric intakes and endocrine-mediated or strain specific tumors and support FDA's and others' positions that use of diet optimization in chronic toxicity and carcinogenicity rodent bioassays has the potential to remarkably improve the scientific quality and relevance of these studies.
Abstract: Controversy regarding the use of ad libitum feeding in chronic rodent toxicity studies will soon result in issue of a FDA Points to Consider document. Caloric intakes are now recognized to be important uncontrolled variables in bioassays because rodents chronically fed ad libitum become obese, reproductively senile and have increased incidences of age-related diseases, higher tumor burdens and decreased survival. The available literature suggests that ad libitum feeding neither optimizes the health and well-being of rodents nor provides the best model for use in evaluation of pharmacological and toxicological profiles. Use of an optimized diet, restricted in terms of caloric intakes, has been proposed for chronic toxicity and carcinogenicity studies in rodents. It is suggested that limiting caloric intakes to 50-80% of ad libitum consumption would result in lower body weights, decreased tumor incidences and prolonged survival in the controls. To evaluate the influence of diet on chronic toxicity and carcinogenicity studies in rats, two 104-week studies were conducted. These studies consisted of 280 CD Sprague-Dawley and 280 Fischer-344 rats fed ad libitum, and 140 CD Sprague-Dawley and 140 Fischer-344 rats fed a diet that was optimized by limiting caloric intakes by 15-35%. Both diets consisted of certified commercial diet in meal form. The optimized diet reduced weight gain approximately 50% after 100 weeks. Clinical chemistry and hematology parameters showed negligible effects of reduced diet, with the exception that serum triglycerides were lower in males and females in both strains at weeks 52 and 104. The ad libitum-fed animals had a higher incidence of pseudopregnancy, aggressiveness, foot sores and abscesses than the animals fed an optimized diet. These effects were more pronounced in the CD Sprague-Dawley rats than in the Fischer-344 rats. At the completion of the 104-week study, survival in the ad libitum fed CD Sprague-Dawley rats was approximately one-half that of the animals fed an optimized diet (39% versus 76%). The difference in survival between Fischer-344 rats fed ad libitum and those fed an optimized diet was less pronounced (78% versus 89%). A reduced incidence of palpable tissue masses in the ad libitum-fed CD Sprague-Dawley rats versus the animals fed an optimized diet reflected inability to detect small masses in the obese ad libitum-fed animals. In contrast, the leaner Fischer-344 ad libitum-fed animals had an increased incidence of palpable tissue masses. After 52 weeks, 40 animals from each strain and feeding regimen were killed and subjected to complete necropsy and histopathological examination; the remainder of the survivors was examined at the completion of the study (104 weeks). Use of an optimized diet substantially reduced the incidences of endocrine-mediated tumors in both rat strains and delayed the onset of leukemia in Fischer-344 rats. These results indicate the need to further investigate the relationship of increased caloric intakes and endocrine-mediated or strain specific tumors and support FDA's and others' positions that use of diet optimization in chronic toxicity and carcinogenicity rodent bioassays has the potential to remarkably improve the scientific quality and relevance of these studies. It also identified that the small increases in cost associated with diet optimization are far exceeded by the advantages of increased survival of animals, reduced intercurrent disease and rumor burdens, and increased ease of histopathological processing and evaluation.
33 citations
TL;DR: The objectives of these studies were to determine the irritation and sensitizing potential of these two compounds when applied topically to B6C3F1 mice and to identify both irritants and contact sensitizers.
Abstract: Dicyclohexylcarbodiimide (DCC) and diisopropylcarbodiimide (DIC) are two commonly used coupling reagents in protein synthesis resulting in exposure of individuals in chemical and pharmaceutical industries as well as research laboratories involved in protein synthesis and recombinant DNA techniques. The objectives of these studies were to determine the irritation and sensitizing potential of these two compounds when applied topically to B6C3F1 mice. Sensitization potential was assessed by the Mouse Ear Swelling Test (MEST) and the murine Local Lymph Node Assay (LLNA). Concentrations used in the contact hypersensitivity assays were determined by primary irritancy studies. DCC and DIC were identified as both irritants and contact sensitizers with the MEST being a more sensitive indicator of sensitization potential. The MEST identified DCC as a sensitizer at concentrations as low as 0.006% (w/v) 24 hr and 48 hr post challenge and DIC at 0.3% (w/v) and 1.5% (w/v) 24 and 48 hr post challenge, respectively. In the LLNA, the lowest concentrations yielding a significant response were 0.06% (w/v) for DCC and 10% (w/v) for DIC.
32 citations
TL;DR: The toxicity profile of the antidepressant drug sertraline was determined in a series of preclinical studies in mice, rats, rabbits and dogs and there was no teratogenicity in studies conducted at maternally toxic doses in rats and rabbits.
Abstract: The toxicity profile of the antidepressant drug sertraline was determined in a series of preclinical studies in mice, rats, rabbits and dogs. Acute, subchronic, reproductive, chronic and carcinogenicity studies were conducted by the oral route. The highest doses tested in these studies were the maximum tolerated doses based on clinical signs, decreased food consumption, body weight effects, organ weight changes or clinical/anatomical pathology findings. Genetic toxicity studies were also performed. The liver was identified as a target organ in the mouse, rat and dog. The observed liver findings were consistent with hepatic xenobiotic-metabolizing enzyme induction and included hepatomegaly, hepatocellular hypertrophy, slightly increased serum transaminase activity and proliferation of smooth endoplasmic reticulum. Hepatocellular fatty change, a minimal toxic effect, was seen in mice and rats. There was no teratogenicity in studies conducted at maternally toxic doses in rats and rabbits. Decreased neonatal survival and growth observed in these studies have been previously reported in reproduction studies with other serotonin reuptake inhibitors. Sertraline was not genotoxic in an extensive battery of tests. Carcinogenicity tests were negative in rats, while benign liver tumors were slightly increased in drugtreated male mice. Liver tumors were considered secondary to the enzyme inducing potential of sertraline and not indicative of human risk.
31 citations
TL;DR: Evidence is provided that toremifene is not genotoxic, based on the reported absence of DNA binding in rat liver, and in one in vivo assay, the mouse, erythrocyte micronucleus assay.
Abstract: Toremifene, a second-generation triphenylethylene antiestrogen used clinically in the chemotherapy of breast cancer and some other cancers, differs in its nonclinical toxicology from its first-generation congener tamoxifen. Tamoxifen produces DNA adducts and tumors in rat liver, whereas assays for DNA adduct formation with toremifene have been negative to weakly positive, and toremifene does not produce liver tumors in rats. to evaluate further toremifene for possible genotoxicity, it was tested in three standard, in vitro assay—reversion of bacterial point mutations, unscheduled DNA synthesis in cultured hepatocytes from two rat strains, and cytogenetics of human lymphocytes in primary cultur—and in one in vivo assay, the mouse, erythrocyte micronucleus assay. the three in vitro assays were conducted with toremifene at up to the limit of cytotoxicity (100 to 250 ng/ml, depending on the system). the bacterial mutagenicity and lymphocyte chromosome aberration assays were performed both in the prese...
TL;DR: Although the fetal defects detected following diglyme exposure at 25 ppm were not significantly different from control values, the pattern, type, and incidence of variations were similar to those seen at 100 ppm, suggesting that 25 ppm was an effect level that approaches the lower end of the developmental toxicity response curve.
Abstract: Diglyme (Diethylene glycol dimethyl ether, CAS No. 111-96-6) is a glycol ether which has been used in solvent formulations. To assess the potential developmental toxicity of this chemical, groups of pregnant Crl:CD BR rats were exposed to either 0 (control, room air only), 25, 100, or 400 ppm diglyme by inhalation for 6 hrs/day for Days 7 through 16 or gestation (day on which the copulation plug was detected was designation Day 1 G). All female rats were euthanized on day 21G and the fetuses were examined. An additional group of rats was treated with 25 ppm 2-methoxethanol (2ME) to serve as a positive control and for comparison of relative potencies. Maternal toxicity evident as depressed feed consumption at 400 ppm and increased liver weights at 100 ppm. There were no dams in the 400 ppm group with live fetuses (all litters consisted on resorbed conceptuses). Embryo viability was unaffected by concentrations of diglyme as high as 100 ppm. 2ME produced increased liver weights and depressed feed consumption at 25 ppm. Embryo-fetal toxicity was evident as a concentration-related decrease in fetal weight at diglyme concentrations as high as 100 ppm (and with 2ME). There were no fetuses derived from the 400 ppm diglyme-treated dams. A low incidence of structural malformations was observed in all diglyme groups (as well as with 2ME). The incidence of variations, (primarily delayed skeletal ossification and rudimentary ribs) was increased in the 25 and 100 ppm diglyme groups. The incidence and severity in the diglyme and 2ME groups exposed to 25 ppm was essentially the same suggesting similar potency for producing structural variations. In this study, diglyme was embryolethal at 400 ppm; a level that otherwise was only marginally toxic to the dam. Maternal and fetal toxicity also were demonstrated at 100 ppm. Although the fetal defects detected following diglyme exposure at 25 ppm were not significantly different from control values (with the exception of the incidence of skeletal developmental variations), the pattern, type, and incidence of variations were similar to those seen at 100 ppm, suggesting that 25 ppm was an effect level that approaches the lower end of the developmental toxicity response curve. Therefore, the no-observable-effect level (NOEL) for diglyme exposure in the dam is 25 ppm and a NOEL was not clearly demonstrated for the conceptus.
TL;DR: Controlled studies of human exposures, reports of accidental exposures, and animal studies collectively indicate that exposures to OP nerve agents at levels causing no acute signs or symptoms do not produce chronic illness.
Abstract: Extensive data are available on nerve agents as they relate to low dose toxicity. Highly sensitive in vitro and in vivo mutagenicity and clastogenicity screens as well as subchronic toxicity studies in various animal models have been carried out. the majority of such closely controlled toxicological studies in the United States have been conducted at the National Center for Toxicological Research or at the University of California. Data available on humans exposed to nerve agents are obtained primarily from human volunteer studies and accidental exposures. the former consists of experiments conducted by the U.S. Army between 1958 and 1975. Cases of accidental exposures were occupational hazards of chemical munition production workers. Controlled studies of human exposures, reports of accidental exposures, and animal studies collectively indicate that exposures to OP nerve agents at levels causing no acute signs or symptoms do not produce chronic illness
TL;DR: The patch clamp technique was applied to hippocampal neurons in culture and slices to investigate the effects of VX, sarin and huperzine A on transmitter release and the mechanisms related with such effects.
Abstract: Recent data indicate that the neurotoxic effects of organophosphate compounds, including those of the nerve agents VX and sarin, are not solely due to irreversible cholinesterase inhibition. In this study we applied the patch clamp technique to hippocampal neurons in culture and slices to investigate the effects of VX, sarin and huperzine A on transmitter release and the mechanisms related with such effects. The nerve agents VX and sarin at very low concentrations significantly reduced the evoked release of GABA and glutamate. This effect was dependent of the activation of muscarinic receptors. In the presence or absence of the Na(+)-channel blocker tetrodotoxin (TTX), VX increased the frequency of spontaneous glutamate and GABA-induced postsynaptic currents. The effect of VX on TTX-insensitive spontaneous currents appears to be unrelated to cholinesterase inhibition, because it could be detected even after cholinesterase was blocked by high concentrations of the nerve agent soman. The ability of the nerve gases to decrease evoked release of GABA and increase spontaneous transmitter release may underlie some of the neurotoxic effects of the compounds. Huperzine A did not affect spontaneous or evoked release of GABA and glutamate, suggesting that this compound may be a pure cholinesterase inhibitor and had no effect on postsynaptic GABAA or AMPA receptors.
TL;DR: Results indicate that polystyrene extract does not elicit ER-mediated activity using the Ga14-HEGO/17m5-G-Luc recombinant receptor/reporter gene assay.
Abstract: The purpose of the study was to determine whether polystyrene used in food-contact applications would elicit an estrogenic response when extracts simulating exaggerated conditions of use were subjected to in vivo and in vitro tests. A sample of polystyrene was subjected to extraction conditions that simulate, or exaggerate, the actual food-contact uses of polystyrene to maximize the amount of low molecular weight polystyrene extractables. The food-simulating solvent and the time and temperature conditions recommended by the Food and Drug Administration (FDA) were selected to maximize the level of extractable components from polystyrene. The extract was examined for its estrogenic response in vivo using the immature rat uterotrophic assay and in vitro using an estrogen receptor (ER)-mediated recombinant receptor reporter gene assay. In vivo, the uterine weights of juvenile female Sprague Dawley rats (10 rats/group) were determined after oral gavage exposure to the extract (two dosage levels: one represents the maximum potential daily human exposure to polystyrene extractables and the other represents one-tenth of the maximum exposure level), vehicle control (sesame oil), or positive control [diethylstilbestrol (DES), at 200 micrograms/kg body weight]. In addition, five treatment groups were dosed by subcutaneous injection of either estradiol (1, 50, and 500 micrograms/kg body weight) or DES (2 and 200 micrograms/kg body weight). Dosing began on postnatal day (pnd) 21 and continued daily through pnd 23. Body weights were collected at study initiation (pnd 21) and at necropsy (pnd 24). Body weights were not different statistically between treatment groups at study initiation or at necropsy. Uterine wet weights and uterine weights relative to body weights were significantly increased (p < 0.05) for estradiol at 50 and 500 micrograms/kg, DES at 2 and 200 micrograms/kg, and DES at 200 micrograms/kg (oral) over vehicle control. The polystyrene extract had no effect on uterine wet weight or uterine weights relative to body weights at either level tested. An in vitro recombinant estrogen receptor/reporter gene assay that involved transiently transfecting MCF-7 human breast cancer cells with the chimeric human ER, Ga14-HEGO, consisting of the yeast Ga14 DNA binding domain linked to the ligand binding domain of the human ER and a Ga14 response element (17mer)-regulated reporter gene (17m5-G-Luc) was employed. Dose-dependent induction of the reporter gene, 17m5-G-Luc, was observed with the positive control, 17 beta-estradiol (E2). Induction of greater than 100-fold was obtained following incubation of transfected MCF-7 cells with 10 nM E2 for 24 hours. No induction of reporter gene activity was observed with the polystyrene extracts dissolved in dimethylsulfoxide (0.01, 0.1 or 0.01 mg/ml) using the same assay conditions. These results indicate that polystyrene extract does not elicit ER-mediated activity using the Ga14-HEGO/17m5-G-Luc recombinant receptor/reporter gene assay. In conclusion, extracts from polystyrene produced no estrogenic response in either the rat uterotrophic assay or the MCF-7 cell assay for estrogen receptor-mediated activity.
TL;DR: Short and long-term studies support a wide safety margin for D-002, a mixture of higher aliphatic primary alcohol isolated from bees wax with effective antiulcer effects demonstrated in different experimental models.
Abstract: D-002 is a mixture of higher aliphatic primary alcohol isolated from bees wax (Apis mellifera) with effective antiulcer effects demonstrated in different experimental models. Oral toxicity of D-002 (5-5000 mg/kg) was evaluated in sub-acute (14 days), subchronic (90 days) and chronic (1 year) studies in Sprague-Dawley rats from both sexes. There was no treatment-related toxicity. Thus, effects on body weight, food consumption, clinical observations, blood parameters, organ weight ratios and histopathological findings were similar in control and treated groups. These short and long-term studies support a wide safety margin for this product.
TL;DR: It is concluded that low and high doses of the 23 polystyrene oligomer migrates tested did not induce an estrogenic response, and styrene dimer and trimer concentrations were obtained in conformance with EEC Council Directives.
Abstract: The Styrene Steering Committee (SSC) of the European Chemical Industry Council (CEFIC) sponsored this work to address any concern that styrene dimers and trimers that might migrate from polystyrene containers into food could possess some estrogenic activity and thus possibly affect human health. All phases of the study were conducted in conformance with GLP regulations and without knowledge of the oligomer migrates tested. All activities were managed and audited under a third-party contract between the SSC and Argus International.Low and high doses of the styrene oligomer migrates of 23 polystyrene samples [i.e. 9 general purpose polystyrenes (GPPS), 8 high impact polystyrenes (HIPS) and 6 expandable polystyrenes (EPS)] were tested for estrogenicity in an in vivo uterotrophic assay (immature female rat model). This model is considered to be the “gold standard” for use in screening for estrogenic effects because it evaluates both direct and indirect potential effects. the two concentrations of migrates of ...
TL;DR: It is indicated that body weight is not always predictive of uterine weight, that relative uterin weight outlier values occur in each of these rat strains, and that statistically significant differences exist between groups of untreated control animals when outliervalues are included in analyses.
Abstract: Inclusion of biological outlier values was found to bias the results of rat uterotrophic assays towards false negatives, i.e., not identify uterotrophic effects in treated populations. The present investigation was conducted to identify the background variability in the rat uterotrophic assay and to evaluate the need to exclude biological outlier values in untreated control groups. The Styrene Steering Committee (SSC) of the European Chemical Industry Council (CEFIC) co-sponsored this work with Argus Research Laboratories (Argus). The rat uterotrophic response assay originally was used as a pharmacology screen to identify estrogenic agents. Classically, 5 to 10 immature female rats (18 to 22 days of age) are administered an agent for three or four days. At sacrifice on the following day (21 to 26 days of age), the uterus is removed, weighed and a uterine weight/terminal body weight ratio calculated. This in vivo assay has been adapted for use in identifying the potential estrogenicity of chemicals, generally using 10 immature female rats per group, more closely controlling the ages, and adding one or more positive control groups to demonstrate sensitivity and response of the test system. Statistically significant increases in the positive control group means for absolute and relative uterine weights, as compared with the untreated (or vehicle-treated) means, is generally interpreted as identifying a sensitive test system. The untreated (and/or vehicle-treated) control group is then compared with the various test groups, and statistically significant increases in the mean absolute and relative uterine weights are identified as evidence of estrogenicity of the agent. Although not fully described previously, the inherent biological variability existing in both untreated and treated animals, can confound interpretation of the data, especially when numbers are relatively small. Our laboratories have identified that under controlled GLP-compliant conditions, some Wistar rats [randomly assigned (weight-ordered) to groups of ten at 22 +/- 1 days of age, and sacrificed when 26 +/- 1 days of age] in untreated control groups have high relative uterine weights that skew data distributions such that statistically significant differences are not present between untreated control and positive control groups. Based on these observations, further evaluations of untreated control and positive control (DES-DP, 2.5 micrograms/kg, b.i.d.) populations of three rat strains [Wistar--Chbb:THOM-SPF, Wistar--Crl:(WI)BR and Sprague-Dawley--Crl:CD(SD)IBS BR VAF/Plus "International Genetic Standard"] were made to define when such normal findings should be considered biological outliers, and whether outlier values should be excluded from analyses. Our data indicate that body weight is not always predictive of uterine weight, that relative uterine weight outlier values occur in each of these rat strains, and that statistically significant differences exist between groups of untreated control animals when outlier values are included in analyses. Of 98, 60 and 60 untreated control rats in the three respective strains, 11 (11.2%), 16 (26.7%) and 15 (25.0%) had relative uterine weights > or = 0.150%, and 5 (5.1%), 4 (6.7%) and 9 (15.0%) of these rats had relative uterine weights > or = 0.200%, values within the positive control range. All positive control rats attained relative uterine weights > or = 0.100%. Of 50, 60 and 60 positive control rats in the three respective rat strains, 27 (54%), 47 (78.3%) and 36 (60%) had relative uterine weights > or = 0.200%, 9 (18%), 2 (3.3%) and 7 (11.7%) had relative uterine weights > or = 0.300% and 5 (10%), 1 (1.7%) and 3 (5%) had relative uterine weights > or = 0.400%. The incidences of relative uterine weights > or = 0.300% in the positive control group may indicate the presence of high responders. Histological evaluations of uteri of positive control rats and untreated control rats with relative uterine weights > or = 0.
TL;DR: The data suggest that sustained increases of cell division in the mouse liver may contribute to the increases in liver tumors, and the transient increase in rat liver suggests that this is not sufficient to enhance tumor development.
Abstract: In a previous study, p-dichlorobenzene (pDCB), which is associated with tumorigenicity in male rat kidney and livers of mice of both genders, was found to produce acute increases in cell proliferation in those tissues. To determine whether sustained cell proliferation in the liver in susceptible species correlated with reported carcinogenic effects, we examined the effect of pDCB on cell proliferation in the livers and toxicity to the glutamine synthetase-expressing hepatocyte (GS+) subpopulation of male B6C3F1C3F1 mice and F344 rats. Mice were exposed for up to 4 weeks to 600, the maximally tolerated dose which increased liver tumors, 300 or 150 mg/kg. Rats were exposed to 300, 150 or 75 mg/kg for up to 4 weeks. In mice, the cumulative replicating fraction (CRF) in the livers of the high dose animals was significantly increased 16-fold at 1 week and 4-fold at 4 weeks. The CRF was also increased at 300 mg/kg at 1 week, but this subsided at 4 weeks. No increase was seen in the low dose group. In ra...
TL;DR: Concerns that chemical warfare agents themselves or in combination with other chemicals may cause long-term damage to nerve and muscle are reviewed and discussed.
Abstract: Concerns that chemical warfare (CW) agents themselves or in combination with other chemicals may cause long-term damage to nerve and muscle are reviewed and discussed. Experiments on mice and hens underway with agent GA and pyridostigmine bromide (PB) and their effects (either separately or together) are presented.
TL;DR: Inhibition of growth studies from H. pylori demonstrated that glycyrrhizic acid elicited dose-dependent bactericidal effect in H.pylori cultures, and this report is the first demonstration of glycyRrhizi acid inhibition of arylamine NAT activity and glycynrhizo-acid inhibition of growth in the bacterium H. Pylori.
Abstract: Arylamine N-acetyltransferase (NAT) activities with 2-aminofluorene (2-AF) and p-aminobenzoic acid (PABA) as substrates were determined in Helicobacter pylori, collected from patients with peptic ulcers. The NAT activity was determined using an acetyl CoA recycling assay and high pressure liquid chromatography. Inhibition of growth studies from H. pylori demonstrated that glycyrrhizic acid elicited dose-dependent bactericidal effect in H. pylori cultures, i.e.; the greater the concentration of glycyrrhizic acid, the greater the inhibition of growth of H. pylori. Cytosols or suspensions of H. pylori with and without selected concentrations of glycyrrhizic acid co-treatment showed different percentages of 2-AF and PABA acetylation. The data indicated that there was decreased NAT activity associated with increased glycyrrhizic acid in H. pylori cytosols and intact cells. For the cytosol and intact bacteria examinations, the apparent values of Km and Vmax were decreased after co-treated with 80 M glycyrrhizic acid. This report is the first demonstration of glycyrrhizic acid inhibition of arylamine NAT activity and glycyrrhizic acid inhibition of growth in the bacterium H. pylori.
TL;DR: The increased toxicity of coumarin or 4-hydroxycoumarin following co-incubation with CHO-treated microsomes indicated that highly toxic epoxide intermediates may be produced from oxidative P-450 metabolism and that epoxide hydrolase may play a role in detoxification of the reactive intermediates.
Abstract: The developmental toxicities of coumarin and hydroxycoumarin metabolites were evaluated using FETAX. Young X. laevis embryos were exposed to coumarin, 4-hydroxycoumarin, and 7-hydroxycoumarin in each of two separate concentration-response experiments with and without an exogenous metabolic activation system (MAS) and/or inhibited MAS. The MAS was treated with carbon monoxide (CO), cimetidine (CIM), or ellipticine (ELL) to selectively modulate cytochrome P-450 activity. The MAS was also treated with cyclohexene oxide (CHO) to selectively modulate epoxide hydrolase activity. Without the MAS or inhibited MAS, coumarin and 7-hydroxycoumarin were nearly equitoxic, whereas 4-hydroxycoumarin was nearly 2-fold less developmental toxic than coumarin on an equimolar basis. Addition of the MAS and CIM-MAS increased the developmental toxicities of coumarin and, particularly, 4-hydroxycoumarin. Addition of the CHO-MAS greatly increased the developmental toxicity of coumarin and, especially, 4-hydroxycoumarin. ...
TL;DR: A study is being initiated to investigate subtle neurobehavioral effects and neuropathology in rats due to exposure to combinations of low levels of Sarin, N,N-diethyl-m-toluamide, chlorpyrifos, and pyridostigmine bromide.
Abstract: A study is being initiated to investigate subtle neurobehavioral effects and neuropathology in rats due to exposure to combinations of low levels of Sarin (GB), N,N-diethyl-m-toluamide (DEET), chlorpyrifos (CPF), and pyridostigmine bromide (PB). A similar study is being initiated in rhesus monkeys to investigate neurophysiologic effects and neuromuscular pathology due to exposure to a combination of GB, DEET, CPF, and PB, along with vaccination with botulinum toxoid. A description of these studies is presented.
TL;DR: The results of the homogeneity, stability and concentration analyses of the styrene dimers and trimers in the migrates indicated that the concentrations of migrants were highest as the result of 50% aqueous ethanol extraction of HIPS test Bars followed by GPPS test bars and EPS test foam parts.
Abstract: An oligostyrene-like product (F2L5250) was reported to have estrogen-like activity (statistically significant increases in means for absolute uterine weight and the ratios of the uterine weight to terminal body weight) in juvenile female rats provided a dietary concentration of 100 ppm F2L5250 for four consecutive days. the highest no-effect-level (NOEL) for estrogenic activity was 80 ppm in the diet, corresponding to a daily intake of 13.3 mg F2L5250/kg.Although it is unlikely that such estrogenic tetramers would occur in commercial polystyrene, the Styrene Steering Committee (SSC) of the European Chemical Industry Council (CEFIC) sponsored the current extensive project to address any concern that human consumption of styrene oligomers migrating from polystyrene containers into food, e.g., from packaged yoghurt, or from the use of EPS coffee cups and related products, might affect human health. to ensure confidentiality and compliance with the highest scientific and regulatory standards, the entire proje...
TL;DR: Cardiac sensitization to adrenaline is a phenomenon associated with the inhalation of a number of unsubstituted and halogenated hydrocarbons and CF3I and C3F7I are potent cardiac sensitizers in the adrenaline-challenged dog model.
Abstract: Trifluoroiodomethane (CF3I) and 1,1,2,2,3,3,3-heptafluoro-1-iodopropane (C3F7I) have been considered as replacement candidates for halon fire suppressants due to their excellent fire extinguishant capabilities and low ozone depletion potential compared to halon fire extinguishants in use currently As part of the process to develop environmental and health effects criteria for halon substitutes, a cardiac sensitization test was conducted in beagle dogs Cardiac sensitization to adrenaline is a phenomenon associated with the inhalation of a number of unsubstituted and halogenated hydrocarbons Adrenaline was administered by intravenous injection before and during inhalation of the test substance CF3I was administered to dogs at concentrations in air of 01, 02, 04 or 1% v/v At each of 04 and 10% CF3I, the first dog exposed developed fatal ventricular fibrillation, and no further dogs were exposed at these concentrations There was no cardiac sensitization at 01 or 02% CF3I For the C3F7I ex
TL;DR: It is concluded that reproduction in rats was not altered by repeated inhalation exposure to up to 1.0 mg/L DBE, a concentration that produced both body weight and histologic effects in parental rats.
Abstract: Groups of 20 male and 20 female Crl:CD(SD)BR rats were exposed to Dibasic Esters (DBE) at concentrations of 0 (control), 0.16, 0.40 (maximum attainable vapor), or 1.0 mg/L (aerosol). Exposures were conducted for 6 hours/day, 5 days/week for 14 weeks (pre-breeding) then 7 days/week for 8 weeks (through breeding, gestation, and lactation). The exposures were interrupted for female rats between gestation day 19 and postpartum day 3. Gestation day 1 was defined as the day a copulatory plug was found, postpartum day 1 was defined as the day of birth. No significant differences were observed between control and test rats with respect to mating performance, fertility, length of gestation, or progeny numbers, structure, and viability. Body weights of parental rats and of their offspring were reduced at 1.0 mg/L. The only histopathologic changes detected were in the nasal tissues of the parental rats, where an exposure-related increase in squamous metaplasia in the olfactory epithelium was observed. There was an increase in liver-to-body weight ratios in the two higher parental exposure groups and an increase in the lung-to-body weight ratio also seen at 1.0 mg/L. It is concluded that reproduction in rats was not altered by repeated inhalation exposure to up to 1.0 mg/L DBE, a concentration that produced both body weight and histologic effects in parental rats.
TL;DR: This report is the first demonstration to show that aspirin can decrease N-acetyltransferase activity in the bacterium K. pneumoniae.
Abstract: This study was designed to assess the effects of aspirin on arylamine N-acetyltransferase (NAT) activities in the bacterium Klebsiella pneumoniae using high performance liquid chromatography to measure the acetylation of 2-aminofluorene (2-AF) with or without aspirin. Cytosols or suspensions of K. pneumoniae with or without specific concentrations of aspirin co-treatment showed different percentages of 2-AF acetylation. the data indicated that there was decreased NAT activity associated with increased levels of aspirin in K. pneumoniae cytosols and in intact bacteria. For the cytosol examination, the apparent values of Km and Vmax decreased 0.59-and 0.58-fold after co-treated with 40 aM aspirin, respectively, for 2-AF. For the intact bacteria examination, the apparent values of Km and Vmax decreased 0.60-and 0.67-fold after co-treated with 40 aM aspirin, respectively, for 2-AF. This report is the first demonstration to show that aspirin can decrease N-acetyltransferase activity in the bacterium K....
TL;DR: It is likely that elevation of serum NO2-/NO3- levels may cause myocardial toxicity by alerting rat CV NO pathway, and CsA inhibited cNOS activity of rat ventricles and failed to bring about changes in their iNOSactivity.
Abstract: Cyclosporin A (CsA), an immunosuppressive agent is known to induce cellular toxic effects by alerting calcium homeostasis. Nitric oxide (NO) has been implicated in a number of physiologic roles in the mammalian cardiovascular system (CVS). The aim of our present study is to investigate the effects of CsA on the rat CV NO pathway. We measured iNOS and cNOS activities in the 100,000 g soluble fraction of ventricles and serum nitrite (NO2-) and nitrite (NO3-) levels in rats treated with 25 mg/kg or 50 mg/kg body weight of CsA/24 hr in olive oil. CsA inhibited cNOS activity of rat ventricles and failed to bring about changes in their iNOS activity. Serum NO2-/NO3- levels were elevated in CsA treated tars. Most of these changes were found to be statistically significant (P < 0.01) at 50 mg/kg body wt of CsA. It is likely that elevation of serum NO2-/NO3- levels may cause myocardial toxicity by alerting rat CV NO pathway.
TL;DR: Both human and mouse liver explants tolerated exposure to TCE up to 750 microM without evidence of cytotoxicity and these results are consistent with other reports in describing the greater capacity of mice to metabolize TCE.
Abstract: Human and B6C3F1 mouse liver tissue was exposed to trichloroethylene (TCE) to determine metabolic rate constants. Using a novel volatile exposure system based on precision-cut tissue explants, TCE biometabolism was measured by appearance of a major oxidative product trichloroacetic acid (TCA). TCE metabolic rate was linear in this system to 150 minutes, allowing calculation of Michaelis-Menten kinetic parameters, Km and V max. Both human and mouse liver explants tolerated exposure to TCE up to 750 aM without evidence of cytotoxicity. Km values for mouse and human tissue were 215 and 30.6 aM TCE, respectively, and Vmax estimates were 6.14 and 0.47 ng TCA produced per mg protein min−1, mouse and human, respectively. These results are consistent with other reports in describing the greater capacity of mice to metabolize TCE. Metabolic differences such as these must be considered when interpreting the implications of TCE-induced toxicity in rodent models for human health assessment.
TL;DR: The results suggest that one of the mechanisms of mustard toxicity is via the stimulation of a trypsin/chymotrypsin like serine protease, which is dependent on Ca2+ and new protein synthesis.
Abstract: An in vitro normal human epidermal keratinocytes (NHEK) model was used to study and to characterize the protease stimulated by the mustards 2-chloroethyl ethyl sulphide (CEES), 2-chloro-N-(2-chloroethyl)-N-methylethanamine hydrochloride (nitrogen mustard, HN2), and Bis-2-chloroethyl sulfide (sulfur mustard, HD). The results obtained by using a chromozym (TRY) peptide substrate protease assay showed the optimum mustard concentration and time for protease stimulation to be about 200 microM CEES, 100 microM HN2 or HD, and 16 hours. The mustard-stimulated protease was membrane-bound, and was inhibited by adding a Ca2+ chelator EGTA (2 mM), BAPTA AM (50 microM) or a serine protease inhibitor diisopropyl fluoro-phosphate DFP (1 mM), or a protein synthesis inhibitor cycloheximide (10 microM) in the extracellular medium. These results suggest that one of the mechanisms of mustard toxicity is via the stimulation of a trypsin/chymotrypsin like serine protease, which is dependent on Ca2+ and new protein synthesis. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed a mustard-stimulated approximately equal to 70-80 KDa protein band that was associated with protease activity which was inhibitable by EGTA, BAPTA, DFP or cycloheximide. This mustard-stimulated protein (protease) may serve as a diagnostic tool for mustard exposure as well as an assay for screening prospective antivesicant protease inhibitor drugs.