Jane Adams

NTP-CERHR expert panel report on the reproductive and developmental toxicity of bisphenol A.

Robert E. Chapin, Jane Adams, Kim Boekelheide, L. Earl Gray Jr, Simon W. Hayward, Peter S.J. Lees, Barry S. McIntyre, Kenneth M. Portier, Teresa M. Schnorr, Sherry G. Selevan, John G. Vandenbergh, and Susan R. Woskie Pfizer, Inc., Groton, CT University of Massachusetts, Boston, MA Brown University, Providence, RI U.S. Environmental Protection Agency, Research Triangle Park, NC Vanderbilt University Medical Center, Nashville, TN Johns Hopkins University, Baltimore, MD Schering Plough Research Institute, Summit, NJ American Cancer Society, Atlanta, GA National Institute for Occupational Safety and Health, Cincinnati, OH U.S. Public Health Service (Ret), Silver Spring, MD North Carolina State University, Raleigh, NC University of Massachusetts, Lowell, MA

Pattern of Malformations in the Children of Women Treated with Carbamazepine during Pregnancy

In an attempt to determine whether and to what extent carbamazepine is teratogenic, we evaluated eight children whom we identified retrospectively as having had prenatal exposure to carbamazepine alone or in combination with a variety of anticonvulsants other than phenytoin. In addition, in a prospective study, we documented the outcome of the pregnancies of 72 women who contacted us early in pregnancy because they were concerned about the potential teratogenicity of carbamazepine. A pattern of malformation, the principal features of which are minor craniofacial defects and fingernail hypoplasia, and of developmental delay was identified in the eight children retrospectively ascertained to have been exposed to carbamazepine in utero; this pattern was subsequently confirmed through the evaluation of 48 children born alive to the women in the prospective study. That carbamazepine itself is teratogenic is indicated by the incidence of craniofacial defects (11 percent), fingernail hypoplasia (26 percent), and developmental delay (20 percent) in the 35 live-born children of the women in the prospective study who were exposed prenatally to carbamazepine alone. The similarity between the children exposed prenatally to carbamazepine and those with the fetal hydantoin syndrome is probably related to the fact that both drugs are metabolized through the arene oxide pathway and raises the possibility that it is the epoxide intermediate rather than the specific drug itself that is the teratogenic agent.

Developmental neurotoxicity of anticonvulsants: human and animal evidence on phenytoin.

Most epileptic women delivering children each year take anticonvulsants throughout pregnancy. The teratogenic potential of anticonvulsants is most notable for phenytoin, trimethadione, valproic acid, and carbamazepine. This review focuses on the human and animal evidence for the teratogenicity of phenytoin, with emphasis on neurobehavioral end points. The Fetal Hydantoin Syndrome (FHS) consists of craniofacial defects and any two of the following: pre/postnatal growth deficiency, limb defects, major malformations, and mental deficiency. Available data suggest a prevalence of FHS of 10-30% in infants of women ingesting 100-800 mg/kg of phenytoin during the first trimester or beyond. Unfortunately, data on neurobehavioral development in FHS children is limited. Animal models of FHS have been developed and those focusing on neurobehavioral effects are reviewed. Phenytoin produces multiple behavioral dysfunctions in rat offspring at subteratogenic and nongrowth retarding doses. These behaviorally teratogenic doses produce maternal serum phenytoin concentrations in rats comparable to those found in humans. The dysfunctions in rats are dose-dependent and exposure-period-dependent, but independent of nutritional, maternal rearing, or seizure disorder confounds. Effects include vestibular dysfunction, hyperactivity and deficits in learning and memory. General comparability between the human and animal findings for phenytoin are apparent, however, difficulties with existing studies prevent precise comparisons. Animal studies have not dealt satisfactorily with the potential contribution of epileptic disease state to the FHS, with fetal brain drug concentration determinations, a complete dose-effect range, effects in multiple species (although limited nonhuman primate data exist), site of CNS injury, and the comparability of end points assessed. Human studies have not dealt satisfactorily with issues of the need for prospective study designs, separation of the effects of different anticonvulsants, or adequate long-term follow-up of cases, especially with attention to neuropsychological assessment.

Gestational retinoic acid exposure: a sensitive period for effects on neonatal mortality and cerebellar development.

This is the first in a series of studies investigating the developmental stage-specific neurobehavioral effects of all-trans retinoic acid (RA) exposure. Because high doses of this compound are known to be lethal to the developing organism, we first conducted a dose-response study to identify RA doses that produce low enough levels of gestational/postnatal mortality to make a behavioral analysis possible in survivors. Secondarily, at doses found to produce sufficient survivors on PND 28, effects on body and regional brain weights were examined. Finally, at these doses, effects on somatic malformations were evaluated. Four separate exposure periods were analyzed: gestational days (GD) 8 through 10, 11 through 13, 14 through 16, or postnatal days (PND) 3 through 5. In the postnatal exposure period rat pups were injected (s.c.) with three consecutive daily doses of 0, 5, 10, or 20 mg/kg RA on PND 3 through 5. This postnatal exposure had no detectable effect on survival, body or brain weight. In contrast, there was a marked sensitivity to RA in the GD 11-13 group. Many pups from dams given 10 mg/kg RA PO on GD 11-13 were found dead in the cage on the day of birth, and all surviving pups died within 4 days of birth. Examination of milkbands revealed no evidence of effective suckling in these short-term survivors. The same 10 mg/kg dose at GD 8-10 or GD 14-16 produced much lower mortality and pups appeared to suckle normally. To produce adequate PND 28 survival in the GD 11-13 group, it was necessary to reduce dosage to 2.5 mg/kg daily. Even this lower exposure produced effects on PND 28 body and brain weight, significantly lowering weights of body (84% of control), whole brain (94%), and cerebellum (90%). Cerebellar weight was also depressed as percent of whole brain weight, suggesting an effect focused specifically on this region. RA at 10 or 12.5 mg/kg over GD 14-16 also reduced cerebellar weight (92% and 91% of control, respectively). Thus, exposure on GD 14-16 had effects similar to those seen at GD 11-13, but only at considerably higher doses. In contrast, exposure to RA on GD 8-10 did not affect whole body or brain weight, and of eight brain regions examined, only brain stem weight was reduced (91% of control). The GD 8-10 exposure also differed substantially from later exposures in that it was the only treatment to produce substantial malformations, including exencephaly, eye and skeletal defects. We conclude that gestational exposure to RA produces lethality and regional brain stunting that is dose and developmental stage specific, with a pronounced sensitive period on GD 11-13. In contrast, the GD 8-10 period is most sensitive for production of malformations, albeit at somewhat higher doses.

Behavioral effects of low-dose gestational day 11–13 retinoic acid exposure

In a comparison article we report that maternal PO exposure to 2.5 mg/kg all-trans retinoic acid (RA) daily for 3 consecutive days over gestational days (GD) 11-13 produces a 10% reduction in weight of cerebellum at 4 weeks of age, not accompanied by other malformations. Here we report the results of a preliminary behavioral analysis of offspring exposed gestationally to RA as above. Exposed dams were allowed to deliver normally, and litters were culled to eight pups (4 +/- 1 of each sex) at birth. Both male and female offspring were tested prior to weaning on GD 21. Thereafter females were killed on postnatal day (PND) 28 for verification of RA effects on regional brain weight, and all subsequent behavioral testing was conducted on males. Preweaning tests were restricted to negative geotaxis (PND 8-9) and open field activity (PND 22). Postweaning tests included open field activity (PND 43), auditory startle response (three times, on PNDs 22, 43, and 84), 2-week activity in residential running wheels (PNDs 62-76), complex maze performance for 5 consecutive days (PND 83-87), emergence latency (PND 106), and assessment of the behavioral response to an amphetamine challenge (PND 107). Males were then killed on PND 108 for verification of RA effects on regional brain weights. In this study, RA reduced weight of cerebellum but not striatum. Cerebellar weight was 92% of control values in PND 28 females, and this weight difference had diminished to 95% of control weight by PND 108 in males. There were no treatment effects on negative geotaxis, activity in a small open field, auditory startle amplitude, or latency to enter an illuminated alley from a dark chamber. Maze learning occurred at levels equal to or slightly better than controls. Running wheel activity was enhanced by RA exposure, whereas activity in response to an amphetamine challenge was reduced by such exposure. We conclude that RA doses low enough to produce mild weight reductions in cerebellum, without attendant malformations, can alter behavior. The precise nature of these alterations remains to be elucidated, but the findings reported here suggest that effects may be more pronounced on activity than on learning.

Gestational stage-specific effects of retinoic acid exposure in the rat.

Although, or perhaps because, retinoids are among the earliest known behavioral teratogens, there is still little agreement about the behavioral effects of stage-specific exposure to these compounds. In these studies, pregnant albino rats were gavaged once daily with retinoic acid (RA) for 3 consecutive gestational days (GD), GD 8-10), GD 11-13, or GD 14-16. Dose levels were maximal levels compatible with survival (10, 2.5, or 12.5 mg/kg RA, over GD 8-10, 11-13, and 14-16, respectively). Two studies were conducted. The first assessed the effects of RA exposure on GD 8-10 or 14-16 on regional brain weight and on a large behavioral test battery. The second study assessed the effects of RA exposure on GD 11-13 or GD 14-16 on many of the same variables. Taken together with an earlier study of the behavioral effects of GD 11-13 RA exposure, these studies permit the following conclusions. 1) RA exposure at the above doses at any of the three exposure periods produced an apparent reduction in amphetamine-induced open field activity. 2) RA exposure on GD 14-16 but not earlier produced a robust, replicable rotarod deficit in exposed offspring. 3) RA exposure on GD 11-13, but not earlier or later, increased daytime activity in residential running wheels. 4) RA exposure on GD 11-13 or GD 14-16 but not GD 8-10 reduced weight of cerebellum. 5) No RA effect at any exposure period was seen on maze learning, activity in novel open fields, or on auditory startle.

A Behavioral and Neuroanatomical Investigation of the Lethality Caused by Gestational Day 11-13 Retinoic Acid Exposure

In a companion article, we report that there is a sensitive period for all-trans retinoic acid (RA) lethality on gestational days (GD) 11-13. When dams were given 10 mg/kg RA daily for 3 consecutive days on GD 11-13, a number of pups were found dead in the home cage on the day of birth, and the remainder inevitably died due to an apparent inability to nurse. Here we report a set of experiments further investigating these effects. Dams were exposed PO to 10 mg/kg RA or oil vehicle on GD 11-13. Fetuses were removed by Cesarean section on the afternoon of GD 21, culled, and fostered to non-treated dams that had given normal vaginal delivery a day earlier. Maternal behavior was observed for the first 6 h after fostering. The next morning all surviving pups were given a brief behavioral evaluation, including the ability to attach to the nipple of anesthetized foster dams. At the time of C-section, culls were killed and brains were quickly removed and placed in fixative. A series of paraffin-embedded, cresyl-violet-stained serial sections of a representative brain stem from each litter was prepared. RA exposure did not increase fetal mortality. Treated litters were as large as controls, and virtually all treated fetuses were alive in utero. However, unlike controls, some treated fetuses appeared to have difficulty in initiating spontaneous breathing when delivered by C-section, and considerable physical stimulation was required before normal breathing began. As in the previous report, RA-exposed pups did not have milk in their stomachs after 18 h on the foster dam; further, they did not attach to the maternal nipple, and they had greater difficulty than controls in maintaining an upright posture. Examination of serial sections of the medulla indicated that the hypoglossal nucleus appeared grossly normal in the RA-exposed pups. In contrast, the inferior olive and the area postrema were affected by RA exposure. Both nuclei were normally located, but exhibited reduced cell density and/or intensity of staining. In the inferior olive the dorsal and principal nuclei were primarily affected, to the degree that about one quarter of treated brains had no identifiable principal nucleus. We conclude that RA exposure on GD 11-13 causes abnormal development of cell-dense regions of the medial medulla, and these abnormalities may account for the difficulty these animals experience in beginning spontaneous breathing and in nursing. These breathing and nursing problems in turn almost certainly account for the high mortality seen during natural birth and for the subsequent failure to thrive, respectively.

The neurobehavioral teratology of retinoids: a 50-year history.

This review of the central nervous system (CNS) and behavioral teratology of the retinoids over the last 50 years is a commemorative retrospective organized by decade to show the prominent research focus within each period and the most salient findings. In the 1960s, research focused on the gross CNS malformations associated with exposure and the delineation of dose-response and stage-specific responses in rodent models. Relevant scientific events before and during the 1960s are also discussed to provide the zeitgeist in which the field of neurobehavioral teratology emerged in the 1970s. During this period, studies demonstrated that adverse effects on postnatal behavior could be produced in animals exposed to doses of vitamin A lower than those that were teratogenic or impacted growth. Work during the 1980s showed an overrepresentation of behavioral studies focused on the reliability of screening methods, while the marked effects of human exposure were illustrated in children born to women treated with isotretinoin during pregnancy. The human catastrophe invigorated research during the 1990s, a period when technological advances allowed more elegant examinations of the developing CNS, of biochemical, cellular, and molecular developmental events and regulatory actions, and of the effects of direct genetic manipulations. Likewise, research in the 1990s reflected a reinvigoration of research in neurobehavioral teratology evinced in studies that used animal models to try to better understand human vulnerability. These foci continued in the 2000-2010 period while examinations of the role of retinoids in brain development and lifelong functioning became increasingly sophisticated and broader in scope. This review of the work on retinoids also provides a lens on the more general ontogeny of the field of neurobehavioral teratology. Birth Defects Research (Part A), 2010.

Behavioral outcomes in children exposed prenatally to lamotrigine, valproate, or carbamazepine.

OBJECTIVES To evaluate adaptive behavior outcomes of children prenatally exposed to lamotrigine, valproate, or carbamazepine, and to determine if these outcomes were dose-dependent. METHODS Data were collected from women enrolled in the North American Anti epileptic Drug (AED) Pregnancy Registry who had taken lamotrigine, valproate, or carbamazepine monotherapies throughout pregnancy to suppress seizures. The adaptive behavior of 252 exposed children (including 104 lamotrigine-exposed, 97 carbamazepine-exposed, and 51 valproate-exposed), ages 3- to 6-years-old, was measured using the Vineland-II Adaptive Behavior Scales, administered to each mother by telephone. Mean Adaptive Behavior Composite (ABC), domain standard scores for communication, daily living, socialization and motor skills, and adaptive levels were analyzed and correlated with first trimester drug dose. RESULTS After adjusting for maternal age, education, folate use, cigarette and alcohol exposure, gestational age, and birth weight by propensity score analysis, the mean ABC score for valproate-exposed children was 95.6 (95% CI [91, 101]), versus 100.8 (95% CI [98, 103]) and 103.5 (95% CI [101, 106]) for carbamazepine- and lamotrigine-exposed children, respectively (ANOVA; p=0.017). Significant differences were observed among the three drug groups in the ABC (p=0.017), socialization (p=0.026), and motor (p=0.018) domains, with a trend toward significance in the communication domain (p=0.053). Valproate-exposed children scored lowest and lamotrigine-exposed children scored highest in every category. Valproate-exposed children were most likely to perform at a low or moderately low adaptive level in each category. Higher valproate dose was associated with significantly lower ABC (p=0.020), socialization (p=0.009), and motor (p=0.041) scores before adjusting for confounders. After adjusting for the above variables, increasing VPA dose was associated with decreasing Vineland scores in all domains, but the relationships were not statistically significant. No dose effect was observed for carbamazepine or lamotrigine. CONCLUSIONS Unlike carbamazepine and lamotrigine, prenatal valproate exposure was associated with adaptive behavior impairments with specific deficits in socialization and motor function, along with a relative weakness in communication. Increasing valproate dose was associated with a decline in adaptive functioning. This finding of a linear dose-dependent teratogenic effect suggests that valproate should be avoided at any dose during pregnancy. However, some women with epilepsy controlled only by valproate will decide, in consultation with their provider, that the benefits of continuing valproate during pregnancy outweigh the fetal risks. Faced with difficult choices, clinicians should be supportive as these patients consider their options.

Similarities in genetic mental retardation and neuroteratogenic syndromes

Principles and mechanisms of neurobehavioral teratogenesis are used to show commonalities between manifestations of abnormal development consequent to genetic abnormality or teratogenic exposure. A comparison and contrast of both the neuropathological and neuropsychological characteristics of children with early embryonic exposure to isotretinoin (Accutane) or with selected mental retardation syndromes is presented. Putative mechanisms of retinoid teratogenesis through the disruption of normal retinoid-triggered embryogenesis and the alteration of homeobox gene expression are discussed. Interference with homeobox gene expression as an avenue to the perturbation of early developmental processes and the production of hindbrain and craniofacial abnormalities is then proposed as a common basis for the translation and expression of several genetic mental retardation syndromes. Finally, dose-response effects and other modulators of vulnerability to abnormal development are used to provide a conceptual framework for the understanding of variability in the expression of genetically caused abnormalities.