Teratogenicity In Animals Research Articles

The effects of marginal maternal vitamin A status on penta‐brominated diphenyl ether mixture‐induced alterations in maternal and conceptal vitamin A and fetal development in the Sprague Dawley rat

Polybrominated diphenyl ether (PBDE) toxicity in rodents can be associated with disruptions in endocrine signaling. We previously reported that the penta-BDE mixture, DE-71, disrupts thyroid hormones and vitamin A metabolism in rats during lactation, and that this disruption is amplified in animals fed diets marginal in vitamin A. The ability of the DE-71 to disrupt vitamin A metabolism during the prenatal period has not been evaluated. While penta-BDE mixtures are not strong teratogens in pregnant animals fed standard commercial laboratory diets, we hypothesized that they could be teratogenic under conditions of marginal vitamin A status. rats were fed diets containing 0.4 retinyl equivalents (RE, marginal) or 4.0 RE (adequate) of vitamin A per gram of diet. Pregnant animals were exposed to DE-71 (0, 6, 18, 60, or 120 mg/kg) from gestation days (GD) 6-11.5, or on GD 6-19.5. DE-71 treatment resulted in dose-responsive reductions in maternal thyroid hormone and markers of vitamin A metabolism, with the latter reduction amplified in marginal vitamin A dams. Fetuses from marginal vitamin A, DE-71-exposed dams exhibited a dose-responsive increase in liver retinol binding protein levels. DE-71 treatment did not result in gross malformations; however, consistent with our hypothesis, GD 20 fetal weights were lower, and skeletal ossification was less when DE-71 exposure occurred concomitant with a marginal vitamin A status. For several endpoints, observable effects were evident at the lowest dose tested, consistent with a dose-response trend. The results of this study support the concept that marginal vitamin A status enhances the disruptive effects of DE-71 during prenatal development.

Introduction–Decision points in epilepsy: Bedside to bench

Introduction–Decision points in epilepsy: Bedside to bench

Developmental toxicity of indium: Embryotoxicity and teratogenicity in experimental animals

Indium, a precious metal classified in group 13 (IIIB) in the periodic table, has been used increasingly in the semiconductor industry. Because indium is a rare metal, technology for indium recycling from transparent conducting films for liquid crystal displays is desired, and its safety evaluation is becoming increasingly necessary. The developmental toxicity of indium in experimental animals was summarized. The intravenous or oral administration of indium to pregnant animals causes growth inhibition and the death of embryos in hamsters, rats, and mice. The intravenous administration of indium to pregnant animals causes embryonic or fetal malformation, mainly involving digit and tail deformities, in hamsters and rats. The oral administration of indium also induces fetal malformation in rats and rabbits, but requires higher doses. No teratogenicity has been observed in mice. Caudal hypoplasia, probably due to excessive cell loss by increased apoptosis in the tailbud, in the early postimplantation stage was considered to account for indium-induced tail malformation as a possible pathogenetic mechanism. Findings from in vitro experiments indicated that the embryotoxicity of indium could have direct effects on the conceptuses. Toxicokinetic studies showed that the embryonic exposure concentration was more critical than the exposure time regarding the embryotoxicity of indium. It is considered from these findings that the risk of the developmental toxicity of indium in humans is low, unless an accidentally high level of exposure or unknown toxic interaction occurs because of possible human exposure routes and levels (i.e. oral, very low-level exposure).

Is Diagnostic Ultrasound Harmful to the Fetus?

Ultrasound is the most important diagnostic modality in modern obstetrics. Theoretically, it may induce adverse effects in fetuses by either thermal or non-thermal effects. Hyperthermia is a recognized teratogen in animals. However, no confirmed bioeffects caused by exposure at intensities of present diagnostic ultrasound have ever been reported in human fetuses and the benefits of ultrasound overweigh the possible adverse bioeffects. The knowledge and skills of the users are a major determinant of the risk/benefit implications of the use of ultrasound. All users should understand the possible potential risks and receive specialized training in fetal ultrasound imaging. Recently, the use of new modalities such as Doppler and three-dimensional (3D) ultrasound has increased. There are few studies regarding the safety of 3D ultrasound despite rapidly increasing medical and commercial use. It is unacceptable to perform the ultrasound imaging of the fetus for non-medical purposes.

Patulin in food: state-of-the-art and analytical trends

Patulin is a mycotoxin produced by several fungal species of the genera Penicillium and Aspergillus, found on several fruit species and, remarkably, in apples and apple products. Patulin has a broad spectrum of toxicity, including carcinogenicity and teratogenicity in animals. Due to the stability of the molecule, considerable amounts of patulin still remain in apple products after processing. This paper reviews different analytical methods for patulin determination and methods to reduce levels of patulin in apple products as well.

Gastrointestinal hormones (anorexigenic peptide YY and orexigenic ghrelin) influence neural tube development

Gastrointestinal (GI) hormones play an important role in GI secretion, motility, and eating behaviors. It was recently suggested that GI hormones may have a trophic role in GI tract. Here we demonstrate that two principal GI hormones, anorexigenic peptide YY (PYY) and orexigenic ghrelin, affect neural tube development. Chronic administration into the pregnant mice or transgenic overexpression of PYY led to a neural tube defect (NTD) in the embryos that was blocked by ghrelin. PYY Y1 receptor antagonist prevented the occurrence of NTD induced not only by PYY but also by vitamin A, a well-known teratogen in humans and animals. Y1 receptor deficiency also engendered NTDs, indicating the need to maintain normal Y1 receptor signaling. The present study is the first linking GI hormones to the leading cause of infant mortality and provides a novel insight for neurogenesis in which materno-fetal communication through GI hormones appears to be important.

Increased Susceptibility to Phenytoin Teratogenicity: Excessive Generation of Reactive Oxygen Species or Impaired Antioxidant Defense?

Phenytoin is a human and animal teratogen. Accumulating evidence suggests that the teratogenicity is associated with a potential of phenytoin to cause embryonic cardiac arrhythmia and resultant generation of toxic reactive oxygen species via hypoxia-reoxygenation mechanisms. The A/J mouse is more susceptible to phenytoin teratogenicity than other mouse strains. The aim of this study was to investigate whether A/J mice have other antioxidant enzyme activities than C57BL/6J and CD-1 mice. Also, strain differences in phenytoin effects on embryonic heart rate and rhythm were determined. Another objective was to determine whether a spin trapping agent with capacity to capture reactive oxygen species alter the developmental toxicity of phenytoin. Treatment with this agent resulted in a marked decrease in phenytoin teratogenicity, which supports the idea that reactive oxygen species are important mediators for the teratogenic action of phenytoin. The A/J mice embryos were most susceptible to the adverse cardiac effects of phenytoin and had the highest activity of superoxide dismutase and glutathione peroxidase, while the activity of catalase was the same in embryos of the three different strains. The high activities of antioxidant enzymes in the A/J stain indicate that the sensitivity to develop malformations is caused by excessive arrhythmia-related generation of reactive oxygen species rather than impaired antioxidant defense.

Pregnancy Among Patients With Chronic Myeloid Leukemia Treated With Imatinib

Imatinib has potential teratogenicity in animals, but the effect of exposure to imatinib during conception and pregnancy in humans is not known. The records of all patients with chronic myeloid leukemia (CML) treated with imatinib were reviewed. We report the experience on 19 pregnancies involving 18 patients (10 females and eight males) who conceived while receiving imatinib for the treatment of CML. All female patients discontinued therapy immediately on recognition of pregnancy. Three pregnancies (involving two female patients and one male patient) ended in spontaneous abortion, and one patient had an elective abortion. All other pregnancies were uneventful. Two of the 16 babies had minor abnormalities at or shortly after birth (hypospadias in one baby and rotation of small intestine in one baby) that were surgically repaired. All babies have continued normal growth and development. Among female patients who interrupted therapy, five of nine in complete hematologic remission (CHR) at the time of treatment interruption eventually lost CHR, and six experienced an increase in Philadelphia chromosome-positive metaphases. At a median of 18 months after resuming therapy with imatinib, eight patients had a cytogenetic response (complete in three patients). Although there is no evidence that a brief exposure to imatinib during conception and pregnancy adversely affects the developing fetus, most patients lose their response after treatment interruption. Patients receiving imatinib should be advised to practice adequate contraception.

Interferon beta babies

Many women with multiple sclerosis (MS) ask about the risks of pregnancy before starting (or while on) disease-modifying therapies (DMTs). At least two-thirds of patients with MS are women, and the majority are in their childbearing years at the time of clinical onset and diagnosis. DMTs taken during pregnancy could have direct or indirect toxicity (through immunomodulating properties) on pregnancy outcome. High doses of interferon beta (IFNβ) are abortifacient in monkeys, but studies of teratogenicity in animals are limited by the rapid appearance of antibodies to human IFNβ (product information). Therefore, pregnancy outcome after in utero exposure to DMTs is important, particularly because DMTs are increasingly initiated early in the course of MS. In this issue of Neurology , two articles provide data on pregnancy outcome after in utero exposure to IFNβ.1,2 Sandberg-Wollheim et al.1 provide the first systematic and comprehensive analysis of pregnancy frequency and outcome, combining data from several randomized clinical trials of IFNβ-1a. Because allocation of treatment (IFNβ-1a at any dose vs …

Phenytoin teratogenicity: Hypoxia marker and effects on embryonic heart rhythm suggest an hERG-related mechanism

The antiepileptic drug phenytoin (PHT) is a human and animal teratogen. The teratogenicity has been linked to PHT-induced embryonic cardiac arrhythmia and hypoxic damage during a period when regulation of embryonic heart rhythm is highly dependent on a specific K(+) ion current (I(Kr)). PHT has been shown to inhibit I(Kr). The aims of this study were to investigate whether teratogenic doses cause embryonic hypoxia during and after the I(Kr) susceptible period and to further characterize PHT effects on embryonic heart rhythm. Pregnant C57BL mice were administered the hypoxia marker pimonidazole followed by PHT or saline (controls) on GD 10 or GD 15. The embryos were fixed and sectioned, and the immunostained sections were analyzed with a computer assisted image analysis. Effects of PHT (0-250 microM) on heart rhythm in GD 10 embryos cultured in vitro were videotaped and then analyzed by using a digitalization technique. PHT dose-dependently increased the hypoxia staining (6- and 11-fold after maternal dosing of 100 and 150 mg/kg, respectively) during the period I(Kr) is expressed and functional (GD 10). In contrast, there were no differences between the PHT doses in hypoxia staining, and much less pronounced hypoxia after this period (GD 15). With increasing PHT concentrations, increased length of the interval (bradycardia) and large variations in length between individual heartbeats (arrhythmia) were recorded. PHT induced bradycardia/arrhythmia and severe embryonic hypoxia during the I(Kr) susceptible period, supporting the idea of an I(Kr)-arrhythmia-hypoxia-related teratogenic mechanism.

Toxicity of novel anti-hepatitis drug bicyclol: A preclinical study

To study the toxicity of bicyclol to animals. Acute toxicity test was performed in Kunming strain mice that were orally given bicyclol at the doses of 3 and 5 g/kg body weight, respectively. Wistar rats were orally administered bicyclol at a dose of 5 g/kg body weight. Death and clinical symptoms of animals were recorded within 7 d. Sub-acute toxicity test was carried out in rats that were treated with various doses of bicyclol (150, 300, 600 mg/kg) once daily for 14 d. Animal behaviors, blood biochemical markers, blood and urine pictures were examined. Chronic toxicity test was conducted in 80 Wistar rats of both sexes. The animals were orally administered with various doses of bicyclol (150, 300, 600 mg/kg, 100-400 folds corresponding to the proposed therapeutic dose (1.5 mg/(kg.d)) of bicyclol for patients) once daily for 6 mo except for Sunday. The control group was given the same volume of 0.2% sodium carboxyl methylcellulose (Na-CMC). Twenty-one beagle dogs received bicyclol (25, 75, 225 mg/kg, 16.6, 50, 150 folds corresponding to the proposed therapeutic dose of bicyclol for patients) once a day for 6 mo except for Sunday. The body weight, food intake, urine and feces, blood picture, blood biochemical markers, and pathological examination of main organs were determined. Mutagenicity and teratogenicity were determined. Mutagenicity assay included Ames's test, chromosome aberration test in CHL cells and micronucleus test in mice. For the teratogenicity assay, pregnant Wistar rats weighing 200-250 g were treated with 0.2, 1.0 g/kg bicyclol once daily from the 7th d of gestation for 10 d. The oral LD(50) of bicyclol was over 5 g/kg in mice and rats. No noticeable alterations in subacute and chronic toxicity of rats and dogs were demonstrated. No mutagenicity and teratogenicity of bicyclol were found. Bicyclol has no detectable chronic toxicity as well as mutagenicity and teratogenicity in animals.

Additional investigation on the potentiation of phenytoin teratogenicity by fluconazole

Fluconazole (FCZ) is a potent inhibitor of the cytochrome P450 (CYP)-mediated metabolism of the anti-epileptic agent phenytoin (PHT), a well-known human and animal teratogen. It has been postulated that phenytoin must be bioactivated via the CYP system to initiate teratogenesis. In contrast with this view, FCZ pretreatment has been previously shown to result in a potentiation of PHT teratogenesis. The current study was initiated to determine the impact of FCZ pretreatment on PHT exposure levels in maternal and embryonal compartments. HPLC analysis revealed that under a co-dosing FCZ–PHT regimen resulting in enhanced PHT teratogenesis, statistically significant higher PHT levels are detectable in maternal plasma and embryonic tissue in comparison to controls. These results further argue against a role for CYP system in teratogenic bioactivation of PHT.

Cadmium-induced changes in apoptotic gene expression levels and DNA damage in mouse embryos are blocked by zinc.

Cadmium is a potent teratogen in laboratory animals, causing exencephaly when administered at early stages of development. Due to its heterogenicity with respect to molecular targets, the mechanisms behind cadmium toxicity are not well understood. In the present study, C57BL/6 pregnant mice were treated with saline, cadmium, or zinc plus cadmium at 8 days post-coitus and studied 24 h after exposure. Cadmium induced significant DNA damage in the embryonic cells. Cadmium also induced embryonic growth retardation, as well as a significant upregulation of p53, p21, and Bax transcription levels. At the same time, there was a downregulation of Bcl-2, shifting the equilibrium Bcl-2/Bax toward the apoptotic pathway. There was an increase in apoptotically stained cells in the cadmium-treated embryos, and pro-caspase-3 was significantly activated. Zinc pretreatment maintained DNA damage at the control levels. It also prevented cadmium-induced effects on the expression levels of p53 and p21. The cadmium-induced decrease in Bcl-2 was inhibited, whereas the Bax levels were maintained closer to the control values. The Bad transcripts did not change at any experimental condition. Morphologically, zinc could maintain the embryological development, where apoptotic areas were as in the controls, and decrease por-caspase-3 activation. In summary, cadmium administered to pregnant mice increased primary DNA damage and activated the apoptotic pathway. These effects could be ameliorated by zinc pretreatment, and, because of that, it is possible that the mechanisms of cadmium-induced teratogenicity are related to zinc metabolism.

Women in Early Phase Trials: An IRB's Deliberations

he University of Nebraska Medical Center institutional review board (UNMC IRB) recently gave considerable attention to issues concerning respect for persons, justice, and beneficence. Our deliberations were occasioned by review of a protocol of a new biological agent for treatment of Type II diabetes, specifically the protocol's inclusion criteria regarding women of childbearing potential. The study was a randomized Phase I/II study of the safety and efficacy of three doses of a specific agent, compared to placebo, given in combination with other agents over a three-month period in patients with a particular condition. Among the inclusion criteria was a requirement that while on study women of childbearing potential (i.e., premenopausal females capable of becoming pregnant) use either oral contraceptives or an IUD as the only acceptable method of contraception. Prior to the start of study medication, women of childbearing potential must have had a negative urine pregnancy test. Animal teratogenicity studies of the agent had not been completed at the time of the IRB review.

Kinetics and organotropy of some polyfluorinated dibenzo- p-dioxins and dibenzofurans (PFDD/PFDF) in rats

While poly chlorinated dibenzo- p- dioxins and dibenzo furans (PCDD/PCDF) and the corresponding polybrominated congeners must be considered as animal teratogens and carcinogens, little information is available on corresponding poly fluorinated compounds (PFDD/PFDF). Kinetic studies on a few fluorinated dibenzo- p-dioxins and dibenzofurans revealed a rapid elimination, suggesting a much lower toxicity than the corresponding polychlorinated and polybrominated congeners. In order to obtain further clues on the possible toxicity, the kinetics and organ distribution (in liver, thymus and adipose tissue) of a PFDD/PFDF-mixture were studied in Wistar rats after intravenous application. The congeners investigated included four of the 2,3,7,8-substituted, and four of the not-2,3,7,8-substituted dibenzo-p-dioxins, as well as two dibenzofurans. The main result of our studies is the finding that the concentration in the thymus of several of the 2,3,7,8-substituted PFDD/PFDF greatly exceeded that in hepatic tissue. An organotropy quite different from that of the other polyhalogenated congeners must be expected, immunosuppressive effects presumably being the predominant ones. Overall, the elimination half-life of all the PFDD/PFDF studied is considerably shorter than that of the corresponding polychlorinated or polybrominated congeners, in the rat, suggesting a much lower toxicity in this species. No information is available for other species, e.g. nonhuman primates or humans.

Functional alterations in CNS catecholamine systems in adolescence and adulthood after neonatal chlorpyrifos exposure

Chlorpyrifos (CPF), one of the most widely used pesticides, is a neurobehavioral teratogen in animals. We administered CPF to neonatal rats on postnatal days (PN) 1–4 (1 mg/kg) or PN11–14 (5 mg/kg), regimens devoid of overt systemic toxicity. We then examined the impact on catecholaminergic systems in adolescence (PN30) and adulthood (PN60), assessing basal neurotransmitter content and transmitter utilization rates (turnover) in brain regions comprising the major noradrenergic and dopaminergic projections. Although CPF had only sporadic effects on basal norepinephrine and dopamine content, it profoundly suppressed norepinephrine turnover across multiple regions, indicative of net reductions in presynaptic activity. Dopamine turnover showed less consistent effects, with subnormal turnover in some regions and activation in others. We also evaluated whether CPF exposure altered the ability of catecholamine systems to respond to acute cholinergic stimulation, elicited by administration of a single challenge dose of nicotine. In the normal brain, nicotine increases the utilization of norepinephrine and dopamine. With only a few exceptions, animals receiving neonatal CPF exposure showed lasting desensitization of the nicotine response; not only was the activation by nicotine blunted in the CPF group, but in some regions the nicotine response was reversed, eliciting a reduction in transmitter turnover. These results indicate that neonatal CPF exposure produces widespread deficiencies in catecholaminergic synaptic function that persist into adulthood, and that are best revealed by dynamic measures of synaptic activity and responsiveness, as opposed to static markers like basal transmitter levels. The effects seen here are likely to contribute to alterations in behavioral performance that persist or emerge long after the termination of CPF exposure.

Fetotoxicity caused by the interaction between zinc and arsenic in mice.

Arsenic is an environmental pollutant that induces congenital malformations in experimental models and can contribute to human birth defects. The environmental exposure to arsenic is relatively small when compared with the doses required to cause teratogenicity in mice and other laboratory animals. In order to study the action of zinc in the arsenic-induced teratogenicity, in the present work mice were either pretreated with zinc and later with arsenic or were treated simultaneously with zinc and arsenic in vivo and in vitro. Following administration of arsenate on gestation day 8, pregnant females were killed on the 17th day of gestation; maternal and fetal data were collected by laparotomy and used to calculate reproductive parameters. Fetuses were analyzed for the presence of external malformation and, after the appropriate processing, visceral and skeletal analyses were accomplished. Conceptuses were exposed in whole embryo culture to arsenicals on gestation day 8 (3-6 somite stage). After a 26 h culture period, morphological development was assessed. Neither pretreatment with zinc nor simultaneous administration of zinc prevented arsenic teratogenicity in these experimental models.

Induction of apoptosis in cerebellar granule cells by 2,4-dichlorophenoxyacetic acid.

2,4-Dichlorophenoxyacetic acid (2,4-D) and derivatives are herbicides widely used in Argentina and other parts of the world. Exposure to 2,4-D, its ester and salt formulations, have been associated with a range of adverse health effects in humans and different animal species, from embryotoxicity and teratogenicity to neurotoxicity. In this work, we demonstrate that after 24 hs of treatment with 1 and 2 mM 2,4-D there is an induction of apoptosis in cerebellar granule cells (CGC) in culture. However, with 2 mM 2,4-D one population of CGC developed features of apoptosis while another appeared to die by necrosis. This process is associated with an increase in caspase-3 activity after 12 hs of treatment with the herbicide, which is preceded by cytochrome c release from the mitochondria. Treatment of CGC with 2,4-D appears to induce apoptosis by a direct effect on mitochondria producing cytochrome c release and consequently activation of caspase-3, being mitochondrial damage sufficient for triggering the events that may cause apoptosis.

Evaluation of a core battery of tests for detecting behavioral dysfunction of rat offspring induced by retinoic acid: Collaborative work II of the Japanese behavioral teratology committee

ABSTRACT The Japanese Behavioral Teratology Meeting, a satellite meeting of the Japanese Teratology Society, proposed a core battery of tests to detect behavioral teratogens in animals in 1992. The core battery consists of examining maternal body weight, offspring weight, external anomalies, viability, preweaning landmarks of physical development (pinna, incisor and eyelids), preweaning reflex tests (surface righting, negative geotaxis and mid‐air righting), an open‐field test at 5 weeks of age, a water‐filled multiple T‐maze (Biel‐type water maze) test at 6 weeks, a shuttlebox test at 7 weeks and brain weight at termination on postnatal day 56. In order to evaluate the detectability of behavioral dysfunction in rat offspring by this core battery, the first collaborative study was carried out in 1993 using phenytoin. The present, second collaborative study using retinoic acid (RA) was performed in twenty‐eight laboratories to further evaluate the proposed core test battery. Pregnant SD rats received 5 mg/kg RA orally from days 14 to 16 of gestation, and postnatal development of their offspring was evaluated. The effects of RA on offspring were detected as lower viability, increased incidence of minor anomalies in the paw and nail, delayed pinna detachment, negative geotaxis and air righting, and less frequent rearing and grooming behaviors in the open‐field test. However, no effects were observed in the Biel‐type maze and shuttlebox tests. These results suggest that our proposed core battery of tests is useful as a screening method to detect postnatal development disorders, including behavioral dysfunction, in SD rat offspring exposed to RA in utero.

Issues in the Treatment of Epilepsy

Issues in the Treatment of Epilepsy