Absence of reproductive and developmental toxicity in rats following exposure to a 20-kHz or 60-kHz magnetic field

The use of intermediate frequency (IF) magnetic fields (MFs) in occupational equipment and domestic appliances, such as inductive heating cookers, is increasing. The WHO indicated a lack of scientific evidence needed to assess the health risk of exposure to IF MFs. Male and female rats (24/group) were exposed to a 20 kHz, 0.2 mT(rms) or 60 kHz, 0.1 mT(rms) sinusoidal MF for 22 h/day from 14 days prior to and during mating. Copulated females were exposed until gestation day 7 and sacrificed thereafter. Mated males were sacrificed to examine MF exposure effects on spermatogenesis. Reproductive examinations were blinded, and experiments were duplicated per frequency to ensure reproducibility. No statistically significant, exposure-related changes were found in the estrous cycle, copulation and fertility indices, numbers of corpora lutea and implantation sites, or pre- and postimplantation loss. No reproducible changes were observed in sperm count, motility, or morphological abnormality, or in the weights of testes and epididymides after MF exposure. No significant abnormalities were observed in gross pathology or histopathology of the uterus, ovary, testis, and epididymis in the MF- or sham-exposed groups. MF exposure during the preimplantation period was not toxic to fertility or early embryogenesis under the experimental conditions.     

Absence of reproductive and developmental toxicity in rats following oral dosing with nelfinavir

The potential for nelfinavir mesylate (VIRACEPT) to produce reproductive toxicity was evaluated in rats administered oral doses of 200, 500, or 1000mg/kg/day. In the fertility and early embryonic development to implantation study, male rats were treated beginning 28 days prior to mating until necropsy and females for 2 weeks prior to mating and through gestation day (GD) 7. In the pre- and postnatal development study, pregnant rats were treated from GD 6 through lactation day (LD) 20. Selected F(1) pups from this study were evaluated in sensory and behavioral tests and were subsequently mated. Pregnant F(1) females were euthanized on GD 20 and their F(2) fetuses were examined. F(1) animals were not directly dosed with the drug. No treatment-related effects were observed on any male reproductive parameters. Administration of nelfinavir did not produce adverse effects on fertility, pregnancy, embryo-fetal development, parturition, or lactation in the F(0) generation. Similarly, no adverse effects of nelfinavir treatment were observed on pre- and postnatal growth, development, reproductive performance and embryo-fetal development in the F(1) offspring. Based on the results of this study, the no-observed-adverse-effect-level (NOAEL) for developmental and reproductive toxicity in rats was considered to be 1000mg/kg/day, the highest dose tested.     

Acute and subchronic toxicity of 20 kHz and 60 kHz magnetic fields in rats

Despite increasing use of intermediate frequency (IF) magnetic fields (MFs) in occupational and domestic settings, scientific evidence necessary for health risk assessments of IF MF is insufficient. Male and female Crl:CD(SD) rats (12 per sex per group) were exposed to 20 kHz, 0.20 mT(root mean square, rms) or 60 kHz, 0.10 mT(rms) sinusoidal MFs for 22 h day^?1 for 14 days (acute) or 13 weeks (subchronic). Experiments were duplicated for each frequency to ensure outcome reproducibility, and examinations were blinded for quality assurance. All rats survived without significant clinical signs until the end of experiments. Some changes in body weight between the MF‐exposed and control groups were observed over the course of exposure, although the directions of the changes were inconsistent and not statistically significant after subchronic exposure. There were significant differences between MF‐exposed and control groups in some organ weights and parameters in hematology and clinical chemistry, but these were minor in magnitude and not repeated in duplicate experiments. Histopathological findings reflecting toxicity were sporadic. Frequencies of other findings were similar to historic data in this rat strain, and findings had no specific relationship to changes in organ weight or parameters of hematology and clinical chemistry in each animal. The changes observed throughout this study were considered biologically isolated and were attributable to chance associations rather than to MF exposure. The results, in particular the histopathological evidence, indicate an absence of toxicity in IF MF‐exposed rats and do not support the hypothesis that IF MF exposure produces significant toxicity. Copyright © 2015. The Authors. Journal of Applied Toxicology Published by John Wiley & Sons Ltd.     

Evaluation of the reproductive and developmental toxicity of aluminium ammonium sulfate in a two-generation study in rats

Aluminium ammonium sulfate (AAS) was tested for reproductive/developmental toxicity in a two-generation study. Male and female rats were continuously given AAS in drinking water at 0, 50, 500 or 5000 ppm. Water consumption was decreased in all AAS-treated groups, and the body weight of parental animals transiently decreased in the 5000 ppm group. In either generation, no compound-related changes were found in estrous cyclicity, sperm parameters, copulation, fertility and gestation index, number of implantations and live birth pups, sex ratios of pups or viability during the preweaning period. Male and female F1 pups in the 5000 ppm group showed a lower body weight on postnatal day 21, while there were no differences in the birth weight of F1 and F2 pups between the control and AAS-treated groups. Preweaning body weight gain in F2 males and females indicated a similar decreasing tendency at 5000 ppm. In F1 and F2 weanlings, the weight of the liver, spleen and thymus decreased at 5000 ppm, but no histopathological changes were found in these organs. In F1 females in the 5000 ppm group, vaginal opening was delayed slightly. There were no compound-related changes in male preputial separation or in other developmental landmarks. In behavioral tests conducted for F1 animals at 4-6 weeks of age, no compound-related changes were found in spontaneous locomotor activity and performance in a water-filled multiple T-maze. In conclusion, the NOAEL of AAS for two-generation reproductive/developmental toxicity was considered to be 500 ppm in rats. Considering the aluminium content in the basal diet, the total ingested dose of aluminium from drinking water and food in this 500 ppm group was calculated to be 5.35 mg Al/kg bw/day.     

Comparison of the developmental and reproductive toxicity of diethylstilbestrol administered to rats in utero, lactationally, preweaning, or postweaning.

The objective of the study was to determine which period of exposure produces the most marked effects on the reproductive capacity and sexual development of the rat, with particular emphasis on the relative sensitivity of in utero and postnatal exposures. The endocrine active chemical, diethylstilbestrol (DES) was used as an agent known to affect many of the endpoints examined. Hitherto, such comparisons have been made between studies, rather than within a study. Our data will be helpful in the interpretation of future multigenerational assay data. In preliminary studies, DES was shown to be active in the immature rat uterotrophic assay with a lowest detected dose of 0.05 mg DES/kg body weight by sc injection and 10 mg DES/l (1.6 mg DES/kg body weight) by administration in drinking water. A dose of 60 microg DES/l drinking water ( approximately 6.5mg DES/kg body weight/day) was selected for the main study since this represented the midpoint of the drinking water uterotrophic dose response and produced no overt maternal toxicity. The study used 10 groups of concomitantly pregnant animals, including 2 control groups. The first comparison was between the effects of exposure to DES in utero, and exposure from conception to weaning. Another group of animals was exposed to DES in utero and cross-fostered to untreated pregnant females to prevent lactational transfer of DES to pups. Two groups were exposed to DES neonatally, either from birth to postnatal day (PND) 10 (pups thus having only lactational exposure), or from birth until weaning (PND 21; pups thus having both lactational exposure and self-exposure via drinking water). In addition, a dose response study to DES was conducted on animals exposed from weaning to PND 100, when the first phase of the study was terminated. Pups exposed to DES in utero and pups exposed from weaning to PND 100 were bred to assess fertility of the F1 animals and the sexual development of F2 offspring. This last comparison was to determine the extent to which weanling rats could be used in endocrine toxicity studies to assess their potential to show activity in utero. The most sensitive period of exposure for inducing developmental effects in F1 animals was from weaning onwards. The neonatal to weaning period (PND 1-21) was the next most sensitive. Essentially no effects were induced in F1 animals exposed in utero. No effects of any kind were observed in animals only exposed over the early neonatal period of PND 1-10. The mean day of vaginal opening, testes descent, and prepuce separation was only altered in groups where postnatal exposure to DES continued beyond PND 10, or was started at weaning. No changes were observed in anogenital distance or caudal sperm counts. Some changes in organ weights were observed, but the interpretation of these was often confused by concomitant changes in body weight. In general, histopathological examination of tissues yielded no additional information. In breeding studies with animals exposed to DES in utero, or from weaning, reduced litter sizes and marginal advances in the day of vaginal opening were observed in the offspring, together with changes in organ weights. However, no unique sensitivity was noted for exposure in utero. Evaluation of the several exposure periods and the many markers monitored in this study may have individual strengths in individual cases, but when rigorously compared using the reference estrogen DES, many preconceptions regarding their absolute or relative value were not upheld. Further, each of these markers is subject to natural variability, as demonstrated by comparisons made among the 5 separate control groups available in parts of the present study. This variability increases the chance that small changes observed in endocrine toxicity studies employing small group sizes and a single control group, or no concomitant control group, may be artifactual. The most marked effects observed in this study were on the developmental landmarks in the F1 animals induced by exposures after PND 10. Some effects on developmental landmarks and organ weights were observed in F2 animals following exposure either in utero or postweaning. This study therefore does not establish a unique role for exposures in utero or during the early neonatal period.     

Carcinogenicity and chronic toxicity of di-2-ethylhexyl terephthalate (DEHT) following a 2-year dietary exposure in Fischer 344 rats.

The carcinogenicity and chronic toxicity potential of di-2-ethylhexyl terephthalate (DEHT) was assessed in F-344 rats (50/sex/dose) by dietary exposure for 104 weeks. Exposure levels of 0, 1500, 6000 or 12,000 ppm resulted in average daily doses of 79, 324 and 666 mg/kg/day for males and 102, 418 and 901 mg/kg/day for females. Animals were observed daily for clinical signs and detailed physical examinations were performed weekly. Body weight and food consumption were measured at scheduled intervals. During weeks 103-104, urine and blood samples were collected and analyzed. Eyes were examined during week 104 using a binocular indirect ophthalmoscope. At necropsy, organs were weighed and examined macroscopically and microscopically. No histological effects were noted in any organ at any dose and there was no increase in the incidence of any tumor types. Toxic responses were confined to lower weight gains and food conversion efficiency in males and females ingesting 6000 or 12,000 ppm. The severity of a normal geriatric degenerative retinal change was exacerbated in females exposed to 6000 or 12,000 ppm and in males exposed to 12,000 ppm. Therefore, the no-observed effect level (NOEL) for tumorigenicity was 12,000 ppm and the NOEL for chronic toxicity was 1500 ppm.     

Deterioration in brain and heart functions following a single sub-lethal (0.8 LCt50) inhalation exposure of rats to sarin vapor: a putative mechanism of the long term toxicity

The main injuries among victims of the terrorist act in the Tokyo subway resulted from sub-lethal inhalation and whole body exposure to sarin vapor. In order to study the long term effects of such exposure and to simulate these conditions, freely moving rats were exposed to sarin vapor (27.2 ± 1.7 μg/l) for 10 min. About 50% of the rats showed no overt symptoms and the rest had mild to moderate clinical symptoms that subsided within 4 h following exposure. A reduction of weight was noted during the first 3 days with full recovery on the 4th day. Rat's heart was challenged with epinephrine 1 and 6 months post exposure. A significant reduction in the threshold for epinephrine-induced arrhythmia (EPIA) was noted in rats exposed to sarin. A time dependent increase in the kD and Bmax values of muscarinic auto receptors (M2) was recorded in the rat's cortex and striatum. No changes were recorded in the rats' brain trans locator protein (TSPO) levels, concomitant with no observed changes in the animals' performance in A Morris water maze test. A significant increase in open field activity was noted 6 months following exposure to sarin vapor as well as a significant decrease in prostaglandin E₂ (PGE₂) production in the brain. It is speculated that down regulation of the M2 auto receptor function, caused hyper reactivity of the cholinergic system which leads to the changes described above. The continuous reduction in M2 auto-receptor system through an unknown mechanism may be the cause for long lasting decline in sarin-exposed casualties' health.     

Effects on G2/M Phase Cell Cycle Distribution and Aneuploidy Formation of Exposure to a 60 Hz Electromagnetic Field in Combination with Ionizing Radiation or Hydrogen Peroxide in L132 Nontumorigenic Human Lung Epithelial Cells

The aim of the present study was to assess whether exposure to the combination of an extremely low frequency magnetic field (ELF-MF; 60 Hz, 1 mT or 2 mT) with a stress factor, such as ionizing radiation (IR) or H₂O₂, results in genomic instability in non-tumorigenic human lung epithelial L132 cells. To this end, the percentages of G2/M-arrested cells and aneuploid cells were examined. Exposure to 0.5 Gy IR or 0.05 mM H₂O₂ for 9 h resulted in the highest levels of aneuploidy; however, no cells were observed in the subG1 phase, which indicated the absence of apoptotic cell death. Exposure to an ELF-MF alone (1 mT or 2 mT) did not affect the percentages of G2/M-arrested cells, aneuploid cells, or the populations of cells in the subG1 phase. Moreover, when cells were exposed to a 1 mT or 2 mT ELF-MF in combination with IR (0.5 Gy) or H₂O₂ (0.05 mM), the ELF-MF did not further increase the percentages of G2/M-arrested cells or aneuploid cells. These results suggest that ELF-MFs alone do not induce either G2/M arrest or aneuploidy, even when administered in combination with different stressors.