Cyclophosphamide (CP) is one of the best studied teratogens; it produces primarily central nervous system and skeletal anomalies in rats, mice, rabbits, monkeys, and humans. Furthermore, CP is one of the most extensively studied antineoplastic agents. Recent work using in vitro rodent embryo culture has demonstrated that CP must be bioactivated to be teratogenic. This finding extends earlier work showing that CP must be activated to achieve its antineoplastic and mutagenic effects. Activation of CP to its teratogenic, mutagenic, and antineoplastic form is mediated by microsomal cytochrome P-450 monooxygenases, which convert CP to 4-hydroxycyclophosphamide (4OHCP). In the absence of detoxification, 4OHCP spontaneously breaks down to phosphoramide mustard (PM) and acrolein (AC). PM is the CP metabolite believed to be responsible for the antineoplastic and mutagenic effects of CP, whereas AC is thought to cause the side effects associated with CP chemotherapy. Recent work has shown that the teratogenic effects of CP are mediated by both PM and AC. Although it is far from proven, available evidence supports the hypothesis that DNA is the primary target in terms of the teratogenic, mutagenic, and antineoplastic effects of CP. Although the nature of the DNA lesions produced by CP, which are responsible for its teratogenic, mutagenic, and antineoplastic effects, is not completely understood, cross-linking of DNA seems to play a critical role in the antineoplastic properties of CP. Preliminary information obtained from embryos exposed to CP metabolites suggests that, although DNA cross-linking might play a role in CP teratogenesis, metabolite-induced DNA strand breakage and/or induction of mutations might also play a role. Although insights into the molecular mechanisms underlying CP teratogenesis are just beginning to accumulate, the availability of in vitro embryo culture combined with the modern armamentarium of molecular biology will allow teratologists to probe further the molecular aspects of teratogenesis.

The Consumer Product Safety Commission (CPSC) convened a Chronic Hazard Advisory Panel (CHAP) on Phthalates found in children's toys, and childcare products, and in products used by women of childbearing age. The CHAP conducted a risk assessment on phthalates and phthalate substitutes, and made recommendations to either ban, impose an interim ban, or allow the continued use of phthalates and phthalate substitutes in the above products. After a review of the literature, the evaluation included toxic end points of primary concern, biomonitoring results, extant exposure reconstruction, and epidemiological results. The health end points chosen were associated with the rat phthalate syndrome, which is characterized by malformations of the epididymis, vas deferens, seminal vesicles, prostate, external genitalia (hypospadias), and by cryptorchidism (undescended testes), retention of nipples/areolae, and demasculinization (~incomplete masculinization) of the perineum, resulting in reduced anogenital distance. Risk assessment demonstrated that some phthalates should be permanently banned, removed from the banned list, or remain interim banned. Biomonitoring and toxicology data provided the strongest basis for a mixture risk assessment. In contrast, external exposure data were the weakest and need to be upgraded for epidemiological studies and risk assessments. Such studies would focus on routes and sources. The review presents recommendations and uncertainties.

It has been estimated that about 30% of the genes in the human genome are regulated by microRNAs (miRNAs). These are short RNA sequences that can down-regulate the levels of mRNAs or proteins in animals and plants. Genes regulated by miRNAs are called targets. Typically, methods for target prediction are based solely on sequence data and on the structure information. In this paper we propose a Bayesian graphical modeling approach that infers the miRNA regulatory network by integrating expression levels of miRNAs with their potential mRNA targets and, via the prior probability model, with their sequence/structure information. We use a directed graphical model with a particular structure adapted to our data based on biological considerations. We then achieve network inference using stochastic search methods for variable selection that allow us to explore the huge model space via MCMC. A time-dependent coefficients model is also implemented. We consider experimental data from a study on a very well-known developmental toxicant causing neural tube defects, hyperthermia. Some of the pairs of target gene and miRNA we identify seem very plausible and warrant future investigation. Our proposed method is general and can be easily applied to other types of network inference by integrating multiple data sources.

Teratogen-induced cell death is a common event in the pathogenesis associated with tissues destined to be malformed. Although the importance of this cell death is recognized, little information is available concerning the biochemistry of teratogen-induced cell death. We show that three teratogens, hyperthermia, cyclophosphamide and sodium arsenite induce an increase in cell death in day 9.0 mouse embryos with concurrent induction of DNA fragmentation, activation of caspase-3 and the cleavage of poly (ADPribose) polymerase (PARP). Teratogen-induced cell death is also selective, i.e., some cells within a tissue die while others survive. In addition, cells within some tissues die when exposed to teratogens while cells in other tissues are relatively resistant to teratogen-induced cell death. An example of the latter selectivity is seen in the cells of the developing heart, which are resistant to the cytotoxic potential of many teratogens. We show that the absence of cell death in the heart is accompanied by the complete lack of DNA fragmentation, activtion of caspase-3 and the cleavage of PARP.