Exploratory evaluation of several teratogen warning symbols

BACKGROUND: Previous research has noted potential inadequacies in the warning labels and symbols used with some teratogenic medications. A clear teratogen warning symbol represents an important component of risk mitigation for accidental teratogen exposure. METHODS: Several teratogen warning symbols were developed through rapid prototyping and focus groups. A nationally distributed field trial (n = 300) examined the relative effectiveness of 6 candidate symbols, including the symbol in use at the time of the study. Measures included open-ended interpretation, closed-ended preference, and demographic surveys. Each participant was shown a single symbol and asked what it meant, to whom it applied, and what that person should do. Text statements were added to the symbol and participants were asked to reinterpret the warning. Participants were told the intended message of the warning, shown all 6 symbols, and asked to choose the most effective symbol. RESULTS: Four of 6 symbols achieved levels of correct interpretation close to or exceeding the American National Standards Institute (ANSI) benchmark of 85% and none exceeded the ANSI limit of 5% critical confusion. Symbols elicited varying conceptual responses. Respondents considered 1 symbol to be the most effective, by a 4 to 1 margin. Several outcomes varied by age and by ethnicity. CONCLUSIONS: Several symbols emerged as viable alternatives to the current symbol; however, no 1 symbol was clearly found to be the most effective. Instead, the symbol considered "best" depends on the messages that are considered most essential to the warning. Additionally, it appears a symbol without the addition of text can convey most, but possibly not all, of the meaning required of the warning label. Next steps should include further symbol refinement, closer examination of text additions to symbols, and validation of the candidate symbols and warnings through a large-scale field trial.     

Refining teratogen warning symbols for diverse populations

BACKGROUND: The current research reports on efforts to refine the design of recently developed teratogen warning symbols and to examine their interpretation by different populations such as those with low health literacy, adolescents, and individuals who are not fluent in English. METHODS: Alternative symbols identified as most successful in an earlier study were further refined through the use of multiple focus groups and expert review. Six symbols emerged as potential candidates to replace the current symbol. A nationally distributed field trial (n = 700) examined these six alternate teratogen warnings in addition to the symbol presently in use. RESULTS: Five of the alternate warning symbols exceeded the level of correct interpretation elicited by the current symbol. No symbol exceeded the ANSI limit of 5% critical confusion. Two symbols consistently elicited the most accurate responses in terms of message interpretation, target audience, intended action, and perceived consequences of ignoring the warning. CONCLUSIONS: This effort produced at least two viable alternative symbols that appear to be more effective than the current symbol at communicating both the instruction to not take while pregnant and the consequence that exposure could cause birth defects. Several results varied by participant characteristics. Understanding how members of diverse subpopulations might interact with these warnings should be informative to healthcare professionals.     

N-nitroso-N-2-fluorenylacetamide: a new direct-acting mutagen and teratogen

Reaction of N-2-fluorenylacetamide (2-FAA, CAS No. 53-96-3) with nitrous fume (N2O3) in glacial acetic acid at 0 degree C yields N-nitroso-N-2-fluorenylacetamide (N-NO-2-FAA), 3-nitro-N-2-fluorenylacetamide, N-nitroso-3-nitro-N-2-fluorenylacetamide and other compounds. N-NO-2-FAA is the major product (80%) and fairly stable at low temperature (-20 degrees C), but extremely labile at ambient temperature. The chemical structure of N-NO-2-FAA is characterized by spectrometric analysis of its naphthol coupling derivatives. This new compound is highly mutagenic to Salmonella typhimurium TA97, TA98, TA100 and TA1538 and requires no microsomal metabolic activation. The mutagenicity of N-NO-2-FAA in TA98 is higher than that of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG, CAS No. 70-25-7) and N-acetoxy-N-2-fluorenylacetamide (N-AcO-2-FAA). The teratogenic potential of N-NO-2-FAA was studied with white Leghorn chick embryos given a single dose of 1-100 micrograms/egg on day 6 of incubation. A high incidence of flaccid paralysis of the legs and a low incidence of feather, claw and bill malformations were found in the treated group; no such malformed embryos were found in the control group. The teratogenicity of N-NO-2-FAA was found to be weaker than that of MNNG, but comparable to that of N-methyl-N-nitrosourea (CAS No. 684-93-5). N-NO-2-FAA is a strong electrophile and reacts readily with histidine, lysine, cysteine, glutathione, tryptophan, adenosine, cytidine at neutral pH. In contrast to N-AcO-2-FAA, N-NO-2-FAA does not react significantly with guanosine and thymidine. It seems that N-NO-2-FAA is a strong direct-acting mutagen and probably a new prototype of synthetic carcinogen.     

Whole embryo morphometry in teratogen screening

Current methodology in embryo evaluation involves qualitative assessment of razor blade and paraffin serial sections. Presently, no one has applied existing computerized morphometric techniques to examine embryos. A technique has been developed that enables investigators to section embryos at 150 mu, thereby greatly reducing the number of sections and making morphometric analysis possible. This type of analysis permits the precise volumetric determination of several developing organ systems. The aim of this study was to evaluate the feasibility and sensitivity of whole embryo morphometry in teratogen screening. Cadmium chloride, a well-established teratogen, was chosen because of its ability to induce exencephaly in approximately one-half of offspring while having no observable effects on the remaining exposed embryos. It was found that both exencephalic and normal-appearing cadmium-exposed embryos had significantly smaller total cellular, neuroepithelial, otic vesicle, optic assembly, limb bud, and cardiac mesenchyme volumes when compared to controls. Also, the neuroepithelial volume of the exencephalic embryos was significantly smaller than the normal-appearing cadmium-exposed embryos. These results suggest that in addition to inducing exencephaly, cadmium chloride has an overall inhibitory effect on embryonic growth. We have shown that whole embryo morphometry is a sensitive means of evaluating embryonic growth that permitted determination of cadmium-induced aberrations not discernable by currently employed techniques. In light of these results, we feel this technique shows promise for future investigations of known and suspected teratogens.     

Marshall J. Edwards: discoverer of maternal hyperthermia as a human teratogen

In a series of animal studies performed over a career spanning 40 years at the University of Sydney, Professor Marshall J. Edwards investigated the hypothesis that maternal hyperthermia during gestation can be teratogenic to the developing fetus. He is one of few investigators to have discovered a known human teratogen primarily through animal studies. In 1970 he earned his Ph.D. from the University of Sydney, writing a doctoral thesis entitled "A Study of Some Factors Affecting Fertility of Animals with Particular Reference to the Effects of Hyperthermia on Gestation and Prenatal Development of the Guinea-Pig." He went on to prove that hyperthermia-induced malformations in animals involve many organs and structures, particularly the central nervous system. Other defects include craniofacial anomalies, heart defects and hypodactyly, cataracts and coloboma, kyphoscoliosis, renal anomalies, dental agenesis, and abdominal wall defects. In a series of carefully planned and executed experiments, he demonstrated that the type of defect is related to the timing of the hyperthermic insult, and analyzed the underlying mechanisms. Cell death, membrane disruption, vascular disruption, and placental infarction were all implicated in causing embryonic damage. This special article reviews the scientific discoveries and personal philosophy of Marshall J. Edwards, the discoverer of maternal hyperthermia as a human teratogen.     

天堂的危机——野性之河亚马逊——对“聚宝盆”的不同解读

2006年11月．互联网上一则在亚马逊的森林小镇发现黄金的消息．引发了巴西沉寂了20年的最疯狂的淘金热。该金矿位于马瑙斯450公里的阿普镇,金矿纯度98％。于是在短短两个月内一万名淘金客蜂拥而至．掘得黄金150公斤．价值300万美元。     

Hyperthermia as a teratogen: parameters determining hyperthermia-induced head defects in the rat

This study determined the relationship between the duration and extent of temperature elevation, during a critical period of rat embryonic development, and the induction of congenital malformations. Pregnant Sprague-Dawley rats, at 9 days 12 hours gestation (gastrulation stage), were partially immersed in a water bath until their core temperature, monitored by a rectal thermistor probe, was elevated to a nominated temperature. Seven temperatures were tested from 40.5 degrees C to 43.5 degrees C, elevations of 2.0-5.0 degrees C in core temperature. Various durations at each of these temperatures were tested for potential teratogenicity. A single elevation of 5.0 degrees C or 4.5 degrees C needed only a "spike" in duration to be teratogenic, 4.0 degrees C was teratogenic within 5 minutes, 3.5 degrees C within 10 minutes, 3.0 degrees C within 20 minutes, and 2.5 degrees C within 1 hour. An elevation of 2.0 degrees C for 8 hours was not teratogenic. Microphthalmia was the most common malformation at all teratogenic temperatures and was frequently the only malformation seen at the shortest time exposure for a particular temperature. Encephalocele, facial clefting, and maxillary hypoplasia were the other frequently seen malformations. Five control rats were placed in the water bath for 2 hours at 38 degrees C so that their core temperature was not elevated. All the control fetuses were normal. An elevation of 2.5 degrees C for 1 hour was the threshold combination for teratogenesis. As the temperature increased above a 2.5 degrees C elevation the necessary duration of exposure for teratogenesis decreased.     

SB-236057: Critical window of sensitivity study and embryopathy of a potent musculoskeletal teratogen

BACKGROUND: SB-236057 is a potent skeletal teratogen in rodents and rabbits. The study objective was to identify the critical developmental window of compound sensitivity and to characterize the early onset of SB-236057 embryopathy. METHODS: SB-236057 was orally administered to Sprague Dawley dams at 100 mg/kg/day on days 6-7, 8-11, 12-14, or 15-17 postcoitus (pc). The critical window of sensitivity was identified to occur between days 8-11 pc. Dams were then dosed on days 8-11 pc and embryos were evaluated by histochemical procedures on days 11, 13, or 15 pc. RESULTS: Axial malformations were evident by day 11 pc. Analysis of the cartilaginous skeleton revealed missing posterior axial skeletal elements. However, only about one-third of the malformed fetuses exhibited obvious rib and vertebrae abnormalities, and none of the affected fetuses exhibited abnormal appendicular skeletal elements. Expression pattern of sonic hedgehog in the notochord and floor plate was not affected, suggesting ventral midline signaling was not disrupted. Histological analysis demonstrated hypoplastic and/or missing musculature in proximity to the ribs and vertebrae. Caspase 3 analysis revealed no increases in apoptotic cells in the musculature. Confocal analysis of the limbs demonstrated truncated peripheral nerve formation and shortening of the appendicular musculature. CONCLUSIONS: SB-236057 is speculated to alter paraxial mesoderm programming. Many of the skeletal malformations may be caused secondarily from musculature abnormalities, suggesting that the myotome may be particularly sensitive to the compound. Furthermore, the finding that peripheral nerve trajectories were altered along the axis and in the limb suggests that SB-236057 may alter early embryonic signaling pathways necessary for neuronal differentiation/axonal guidance that occur subsequently in embryo-fetal development.     

Mechanisms of action of the congenital diaphragmatic hernia-inducing teratogen nitrofen

Congenital diaphragmatic hernia (CDH) is a developmental anomaly that results in significant mortality and morbidity. The underlying etiology is poorly understood. Insights will arise from an understanding of the mechanisms by which the teratogen nitrofen induces CDH in rodent models. In this study, we use in vitro cell assays in conjunction with whole animal rodent studies to test hypotheses regarding nitrofen's mechanism of action. The first component examined the interaction of nitrofen with various aspects of the retinoid signaling pathway including uptake proteins, binding proteins, receptors, conversion, and degradation enzymes. The second component examined the interactions of nitrofen and vitamins A, C, and E to test the hypothesis that nitrofen was functioning as an antioxidant to interfere with retinoid signaling. Third, we performed a series of experiments examining the interaction of nitrofen and thyroid signaling. Collectively, the data suggest that the primary aspect of retinoid signaling affected by nitrofen is via inhibition of the rate-limiting enzymes controlling retinoic acid synthesis. Retinoid signaling perturbations do not appear to involve oxidative effects of nitrofen. Any substantial roles of nitrofen-induced perturbations of thyroid hormone signaling or receptor function are not supported.