bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of administration time on malformations induced by three anticonvulsant agents in C57BL/6J mice with emphasis on forelimb ectrodactyly
Authors: Collins Michael D. , Walling Karen M. , Resnick Elisabeth , Scott William J.
Published: June 2005

Exposure of C57BL/6J mice to three anticonvulsant derivatives, namely, dimethadione, sodium valproate, and sodium diphenylhydantoin, each induced postaxial forelimb ectrodactyly. The agents were administered at gestational days 9, 9 1/3, 9 2/3, and 10. It was determined that administration at day 9 2/3 induced the highest percentage of forelimb ectrodactyly for each of the three agents. The forelimb ectrodactyly response in the C57BL/6J strain was compared with the A/J strain (Collins et al., Teratology, 41:61–70, 1990); it was found that the C57BL/6J strain was more sensitive to dimethadione and the A/J strain was more sensitive to diphenylhydantoin and sodium valproate. The position of vertebral defects induced by sodium valproate correlated with the time of drug administration. The overall syndrome of malformations induced by the three anticonvulsant agents was relatively similar in the two mouse strains and differed between each of the anticonvulsant agents.
The individual and combined effects of X‐irradiation and hyperthermia on early somite mouse embryos in culture
Authors: Nakashima K. , Kawamata A. , Fujiki I. , Fujiki Y.
Published: June 2005

The effects of 1) X‐irradiation and 2) hyperthermia at a temperature of 43°C individually and in combination have been investigated using cultured 8‐day mouse embryos. BGC3F1 embryos were exposed to 0.3–2.0 Gy of X‐rays, 5–20 min of heating, or 5 min of heating and irradiation at 0.3, 0.6, and 0.9 Gy. Irradiation alone at 0.3 Gy showed no apparent effect on embryonic development, but irradiation at 0.6–2.0 Gy caused a dose‐dependent increase in malformed embryos. Heating alone for 5 min produced no malformed embryos, while heating for 10–20 min caused malformations as a function of heating time. Combined treatments produced higher frequencies (22.2–100%) of malformations than those of the sum of the separate treatments (0–41.7%). Malformations observed were primarily microphthalmia, microcephaly, and open neural tubes. The results indicate that in cultured mouse embryos irradiation combined with a “nonteratogenic dose” of hyperthermia directly exerts an additive effect on formation of the malformed embryos. In addition, a single occurrence of left‐sided tail was produced by hyperthermia alone, while four occurrences were produced in combination with radiation.
Cardiovascular anomalies in chick embryos produced by bis‐diamine in dimethylsulfoxide
Authors: Okishima Takahiro , Takamura Kazushi , Matsuoka Yuji , Ohdo Shozo , Hayakawa Kunio
Published: June 2005

N,N′‐bis(dichloroacetyl)‐1,8‐octamethylenediamine(bis‐diamine) (100 μg) dissolved in dimethylsulfoxide (DMSO) was administered to early developing chick embryos (Hamburger‐Hamilton stage 9‐21) in order to clarify the teratogenic effects on the cardiovascular system and to determine whether bis‐diamine interferes with the migration of neural crest cells.

Of 346 cases, 154 (44.5%) survived. The incidence of cardiovascular anomalies was 149 out of 154 cases (96.8%). Infundibular ventricular septal defect, double outlet right ventricle, and persistent truncus arteriosus were the primary cardiac anomalies observed in this study. A high percentage of these anomalies were accompanied by hypoplasia of the right 6th aortic arch artery and persistent left 4th aortic arch artery. Particularly, administration of bis‐diamine to chick embryos at stage 13 resulted in a high incidence of persistent truncus arteriosus (64.3%).

Bis‐diamine has been suspected to inhibiting the migration of neural crest cells. However, neural crest cells were observed in the tunica media of the great arteries and the truncal valves of persistent truncus arteriosus produced by bis‐diamine in chimeric embryos at stage 13. Morphological changes such as cell death were not observed.
Effects of 4‐hydroperoxycyclophosphamide (4‐OOH‐CP) and 4‐hydroperoxydechlorocyclophosphamide (4‐OOH‐deCICP) on the cell cycle of post implantation rat embryos
Authors: Little Sally A. , Mirkes Philip E.
Published: June 2005

In this study, we used preactivated forms of cyclophosphamide (CP) and dechlorocyclophosphamide (deCICP) to examine the effects of phosphoramide mustard (PM) and acrolein, respectively, on the cell cycle of postimplantation rat embryos. The percentage distribution of cells in the G1/G0, S, and G2/M phases of the cell cycle was determined by flow‐cytometric analysis. At embryotoxic concentrations, 4‐OOH‐CP (PM) induced major cell cycle perturbations whereas 4‐OOH‐deCICP (acrolein) caused no major perturbation of the cell cycle. These data support the hypothesis that the mechanism of the embryotoxic action of PM involves alkylation of DNA, whereas the mechanism of action of acrolein does not. The primary effect of PM on the cell cycle was an initial delay in the S phase followed by a G2/M arrest. At low embryotoxic concentrations of 4‐OOH‐CP, there was apparent reversal of the G2/M arrest; at higher embryotoxic concentrations there was little recovery from the G2/M arrest. The high level of cell death found at higher drug concentrations suggests that prolonged G2/M arrest leads to cell death. Using radiolabeled CP and cell sorting, it was determined that PM predominantly alkylated DNA in the S phase of the cell cycle. Overall, the data from this study support the hypothesis that DNA cross‐links, induced by the alkylation of DNA by PM, induce cell cycle perturbations. Furthermore, these cell cycle alterations may be one of the early steps in the mechanism leading to the embryotoxicity of PM.
Further evidence that arthrogryposis multiplex congenita in the human sometimes is caused by an intrauterine vascular accident
Authors: Robertson Wendy L. , Glinski Lisa P. , Kirkpatrick Susan J. , Pauli Richard M.
Published: June 2005

A 7½‐year‐old girl with arthrogryposis multiplex congenita of the amyoplasia type in association with intestinal atresias, gastroschisis, Möbius anomaly, and hypoplasia of the pectoral, biceps, and deltoid muscles is described. Several combinations of these birth defects have been previously described. There is considerable evidence that gastroschisis, intestinal atresia, Poland sequence, and Möbius anomaly each has a vascular pathogenesis. Based on the associations seen in this child and past reports of more limited, similar cooccurrences, we suggest that arthrogryposis multiplex congenita may sometimes be caused by an intrauterine vascular catastrophe.
Embryonic palatal responses to teratogens in serum‐free organ culture
Authors: Abbott B. D. , Buckalew A. R.
Published: June 2005

This study examines development of rat, mouse, and human embryonic palates in submerged, serum‐free organ culture. The concentration‐response profiles for retinoic acid (RA), triamcinolone (TRI), hydrocortisone (HC), dexamethasone (DEX), and 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) were examined and the mechanisms of clefting in vitro were compared to observed in vivo responses. Craniofacial regions were dissected on gestational day (GD) 12 for mice and GD 14 for rat, and cultured for 3‐4 days in Bigger's BGJb medium in flasks flushed with 50% O2, 45% N2, 5% CO2. Growth and fusion of secondary palates were scored under a dissecting microscope. In serum‐free control medium, mouse and rat palatal fusion occurred within the 4‐day culture period. Supplementing with fetal bovine serum (FBS) in excess of 1% interfered with growth and fusion in control medium. RA significantly inhibited fusion of mouse and rat palates at 5 × 10−9 and 1 × 10−10 M, respectively, with RA‐induced clefting related to abnormal proliferation and differentiation of medial epithelia. In contrast, glucocorticoid‐induced clefting was due to concentration‐dependent inhibition of shelf growth. TRI significantly inhibited fusion at 4 × 10−5 M, and 1 × 10−4 M DEX or HC, inhibited fusion of 19 and 42% of shelves, respectively. The response rate for DEX in the presence of 1% FBS was increased (42% unfused). TCDD clefting was due to altered medial epithelial differentiation and 1 × 10−8 M TCDD affected 36% of CD‐1 mouse, 23% of C57BL/6N mouse, and 47% of F344 rat palates. When the medium was supplemented with 1% FBS, selenium, transferrin, and additional glutamine, the response of C57BL/6N embryos increased to 75%. This rate is similar to that reported for Trowell's‐type cultures with IMEM:F12 medium and 1% FBS. The increased responsiveness to DEX or TCDD in the presence of serum suggests that an unknown factor in serum may be required for full activity. Three human embryonic palatal explants (GD 52 or 53) were cultured for 3‐6 days and fused during culture. The present study demonstrates that serum‐free organ culture supports development of mouse, rat, and human palatal explants. The present study demonstrates the capacity of this organ culture system to model palatogenesis for several species, and to distinguish between various mechanisms of clefting as presented through selected model compounds. This model should be useful for exploring mechanisms of activity at a cellular and molecular level.
Extraembryonic tissue changes induced by 2,3,7,8‐ tetrachlorodibenzo‐p‐dioxin and 2,3,4,7,8‐pentachlorodibenzofuran with a note on direction of maternal blood flow in the labyrinth of C57BL/6N mice
Authors: Khera K. S.
Published: June 2005

Histologic changes in extraembryonic and embryonic tissues induced by 3 or 6 μg 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin/kg (TCDD) or 80 μg 2,3,4,7,8‐pentachlorodibenzofuran/kg/day (4‐PeCDF) were studied 24 h after the last of four daily doses administered orally to C57BL/6N mice on days 10‐13 of pregnancy. Both test compounds ruptured (1) the embryo‐maternal vascular barrier in the labyrinth, which resulted in hemorrhage of embryonic blood into the maternal circulation, (2) the visceral yolk sac membrane with the embryonic blood from the vitelline vessels escaping into the uterine, exocelomic and amniotic cavities, and (3) the maternal vascular spaces of the placental periphery resulting in hemorrhages into the interconceptal space. The role of the hemorrhagic lesions in the induction of cleft palate and hydronephrosis by the two compounds remains to be investigated. The presence of embryonic nucleated erythroblasts that hemorrhaged into the maternal lacunar network allowed the identification of maternal venous channels in the placenta. It revealed that (1) the labyrinth could be tentatively divided into two caudocranially oriented zones, an arterial and a venous zone; (2) the maternal blood in the labyrinthine lacunae circulated from the arterial to the venous zone, somewhat parallel to the uterine axis; and (3) the largest maternal vessels in the center of the placenta hitherto named the “central maternal artery,” was in fact, venous. © 1992 Wiley‐Liss, Inc.
Diagnosis of abnormalities of the human fetus during the first, second, and third trimesters
Authors: Larsen John W.
Published: June 2005

Clinical teratologists will have new challenges during the 1990s as birth defects are diagnosed more frequently than in previous decades. Malformations and genetic disorders will be diagnosed in utero during all three trimesters of pregnancy. The teratologist may participate in or lead a multispecialty group to give the involved family optimal interpretation of test results, counseling, and recommendations regarding subsequent clinical management. © 1992 Wiley‐Liss, Inc.
Toxicity of the methyl isocyanate metabolite S‐(N‐methylcarbamoyl)GSH on mouse embryos in culture
Authors: Guest Ian , Baillie Thomas A. , Varma Daya R.
Published: June 2005

Methyl isocyanate, the chemical involved in the 1984 accident at Bhopal, India, forms a labile conjugate, S‐(N‐methylcarbamoyl)GSH (SMG), by way of a reversible reaction with GSH. We studied the toxicity of SMG on mouse embryos explanted on day 8 of gestation and cultured in rat serum for 42 hr. SMG caused concentration‐dependent decreases in growth and development over the range 0.1–2 mM, without causing significant mortality. At a concentration of 2 mM, SMG completely arrested embryo development, but heartbeat was absent in only one of nine embryos at 42 hr. At a concentration of 0.25 mM, SMG reduced embryo size to 75% and protein content to 63% of the control; 18% of embryos failed to rotate. At this concentration (0.25 mM), which was selected for all other studies, spinal kinks and somite pair distortion in the region of the forelimb were evident in 38% of embryos; no other abnormalities were noted. DNA content of and thymidine incorporation by embryos and yolk sacs was reduced by SMG, although this was more pronounced in the yolk sac than in embryos. At subtoxic concentrations, the L‐cysteine precursor (−)‐2‐oxo‐4‐thiazolidine‐carboxylic acid did not, but GSH did, inhibit embryotoxicity of SMG. It is concluded that SMG exerts embryotoxic and dysmorphogenic effects and may contribute to systemic toxicity of methyl isocyanate. © 1992 Wiley‐Liss, Inc.
Morphological and physiological correlates of unilateral agenesis of the urogenital system in young ovariectomized ACI rats
Authors: Vassilacopoulou Dido , Boylan Elizabeth S.
Published: June 2005

ACI rats are distinguished by a polygenic trait resulting in unilateral agenesis of the urogenital system in 20–30% of animals of both sexes. This report details additional features, both morphological and physiological, which distinguish ACI rats with unilateral agenesis of the reproductive and urinary tracts from the majority of ACI rats that have intact urogenital systems. Young female ACI rats were ovariectomized at 34 days of age and sacrificed 19 days later. A preliminary determination of the urogenital morphology was made at the time of ovariectomy and then confirmed by careful abdominal inspection at necropsy. Data on the time of vaginal opening were obtained at selected intervals prior to sacrifice. At necropsy, the mammary glands were removed and were prepared as stained whole mounts for morphological evaluation; the remaining portions of the reproductive tracts were excised, weighed, fixed, and sectioned for microscopic examination. A majority of animals with unilateral agenesis had mammary glands that had higher degrees of glandular proliferation than the mammary glands of intact rats. Unilateral agenesis animals also possessed significantly thicker and heavier uterine horns, despite having been ovariectomized. Furthermore, rats with unilateral agenesis were found to have an earlier time of vaginal opening than that of their intact counterparts. These features of ovariectomized ACI rats with unilateral agenesis are consistent with an active, extra‐ovarian source of endogenous estrogen. Further investigation of the endocrinological state of animals with unilateral agenesis of the urogenital tract is warranted. Those using this model system for transplacental or endocrinological studies should take into account these distinguishing characteristics of ovariectomized ACI rats with unilateral agenesis when planning experiments and analyzing data from a population of rats with both morphologies. © 1992 Wiley‐Liss, Inc.
Ellagic acid protects rat embryos in culture from the embryotoxic effects of N‐methyl‐N‐nitrosourea
Authors: Frank Anthony A. , Collier John M. , Forsyth Carol S. , Heur Young‐Hun , Stoner Gary D.
Published: June 2005

Ellagic acid is a naturally occurring plant phenol that has demonstrated anticarcinogenic and antimutagenic acitvity in several test systems. Given the common proposed etiopathogenic processes of mutagenesis, carcinogenesis, and teratogenesis induced by genotoxic chemicals, the present study was initiated to determine whether ellagic acid would protect rat embryos in culture from the teratogenic effects of N‐methyl‐N‐nitrosourea (MNU). Ellagic acid alone (as used in these experiments; 50 μM in DMSO) was not embryotoxic. Ellagic acid (50 μM) significantly (P < 0.01) prevented MNU (75 μM)‐induced effects including mortality (absence of heart beat), abnormal formation of the cephalic neural tube derivatives, and delayed differentiation as assessed by a morphological scoring system. These embryoprotective effects were dose responsive. Sequential treatment of embryos with ellagic acid followed by MNU in fresh media also was embryoprotective with no diminution of effect. The site at which ellagic acid interrupts the critical teratogenic events induced by MNU is apparently within the embryo and/or placenta. This model of chemical embryoprotection may be useful in determining the role of cell death and/or mutation in the teratogenic mechanism of action of methylating agents. © 1992 Wiley‐Liss, Inc.
Prevention of tilorone developmental toxicity with progesterone
Authors: Terry Roger D. , Marks Thomas A. , Hamilton Ramon D. , Pitts Thomas W. , Renis Harold E.
Published: June 2005

The immunomodulator tilorone hydrochloride was administered (gastric intubation) once to time‐pregnant Upj:TUC(SD)spf (Sprague‐Dawley) rats in four experiments. In experiment 1, tilorone (250 or 500 mg/kg) was administered on day 10 of gestation. The dams were killed 4 or 72 hr after dosing. Interferon‐like activity and drug levels were determined in maternal blood, spleen, and thymus, as well as in the embryos. In experiment 2, the test groups received progesterone (2 mg/kg), or tilorone (200 or 400 mg/kg), or progesterone and tilorone. The dams from each group were killed 24 or 48 hr after receiving tilorone. Experiment 3 was similar to experiment 2, except that the dams were killed on gestation day 20. In experiment 4, tilorone (400 mg/kg) was administered on gestation day 17, 18, or 19, and the dams were killed 24 hr after dosing or on gestation day 20. In all four experiments, tilorone‐related maternal toxicity (regardless of whether progesterone also was administered) was observed, as characterized by marked decreases in weight gain, the occurrence of clinical signs, and in experiment 1 by decreased thymus weights, 72 hr postdosing. Dose‐related increases in the mean number of dead embryos and in serum interferon titers occurred 72 hr postdosing. In experiment 2, there was an increase in the number of dams in the 400‐mg/kg (tilorone only) group with dead embryos only, 24 hr postdosing; similar results occurred in both the 200‐ and 400‐mg/kg groups, 48 hr postdosing. However, in the groups that also received progesterone, a partial prevention of such embryolethality was evident. In experiment 3, embryotoxicity again was observed in both tilorone‐treated groups, whereas several of the dams that were also given progesterone through day 19 of gestation experienced at least a partial prevention of the embryolethal effects of tilorone. In experiment 4, no fetotoxicity was observed despite the severe maternal toxicity evident. © 1992 Wiley‐Liss, Inc.
Epidemiology of congenital heart disease in Louisiana: An association between race and sex and the prevalence of specific cardiac malformations
Authors: Storch Thomas G. , Mannick Elizabeth E.
Published: June 2005

We hypothesized that susceptibility to the genetic and environmental factors that disrupt cardiac development is associated with race and sex. To evaluate this hypothesis, we asked whether the prevalence of specific cardiac malformations differs by race and sex. We attempted to include all infants born alive in the State of Louisiana from January 1, 1988, through December 31, 1989, and diagnosed by echocardiography, catheterization and/or autopsy within a year of birth as having one of ten specific cardiac malformations. The prevalence of atrioventricular canal defects (AVCD) per 1,000 live births was significantly higher for black females (.744) compared to black males (.198) and for white females (.414) compared to white males (.116). Complete transposition of the great arteries (TGA) was significantly higher for white males (.559) compared to white females (.122); in contrast, TGA was not significantly different for black males (.198) and black females (.169). Obstructive left heart syndrome (OLHS)—aortic stenosis and/or coarctation of the aorta—was significantly higher for white males (.652) compared to white females (.317); in contrast, OLHS was not significantly different for black males (.264) and black females (.169). Single ventricle (SV) was significantly higher for whites (.202) compared to blacks (.067). We did not find that race and sex were associated with differences in the prevalence of tetralogy of Fallot and hypoplastic left heart syndrome. The numbers of infants with anomalous pulmonary venous return, tricuspid atresia, double outlet right ventricle, or truncus arteriosus were too small to measure an association with race and sex. These results demonstrate that the prevalence of a subset of cardiac malformations differs by race and sex. Selective fetal survival and differential susceptibility to cardiac malformations may be associated with these findings. © 1992 Wiley‐Liss, Inc.
The perception of teratogenic risk of cocaine
Authors: Koren Gideon , Gladstone David , Robeson Christine , Robieux Isabelle
Published: June 2005

While there has been a substantial increase in recreational use of cocaine by young adults, conclusive evidence for cocaine teratogenicity in humans in lacking, and even those believing the drug is teratogenic agree that the rates are quite small. While counseling pregnant women on their teratogenic risk, it was our impression that there is an unrealistically high perception of reproductive risk of cocaine. We wished to quantify the perception of teratogenic risk of cocaine by the public, physicians, and by pregnant women who were counseled following gestational exposure to the drug. Women taking cocaine during the first trimester of pregnancy (n = 54), controls with post secondary education (n = 30), and physicians (n = 30) were asked, using a visual analogue scale, to quantify the teratogenic risk of cocaine and the tendency to terminate/contiue the pregnancy after first trimester exposure; in the case of the “public” and physicians this was a hypothetical question. Both physicians and the controls perceived cocaine to be teratogenic (13.4 ± 11% risk of major malformations by physicians, and 56.5 ± 22.8% by the “public”). The controls believed cocaine to be as hazardous as thalidomide (57.2 ± 25.6% risk for thalidomide). Asked whether they would wish to terminate such pregnancy in their family, most physicians (56%) and the controls (70%) had a greater than 50% tendency to terminate. In pregnant patients attending Motherisk, the counseling process resulted in a significant decrease in risk perception of cocaine (from 37.5 ± 20.5% to 17.6 ± 14.2% P<0.0005), and a similar decrease in tendency to terminate pregnancy [from 21/54 (38%) with 50% tendency to terminate to 11 (20%); P = 0.0014]. Postnatal follow‐up revealed that eight women terminated pregnancy while the rest had morphologically and developmentally normal babies. An unrealistically high perception of teratogenic risk of cocaine exists among the controls, physicians, and pregnant women. Physicians' erroneous perception may lead them to offer women unjustified terminations of pregnancy after first trimester exposure to cocaine. Counseling these women during the first trimester is effective in preventing termination of many otherwise wanted pregnancies. © 1992 Wiley‐Liss, Inc.
Process of building biologically based dose–response models for developmental defects
Authors: Gaylor David W. , Razzaghi Mehdi
Published: June 2005

The problem of developing biologically‐based dose–response models is addressed for predicting the prevalence of birth defects at low doses of toxic chemicals administered during pregnancy. To illustrate the process of incorporating biological information, a model is postulated to predict the prevalence of cleft palate for a chemical that reduces embryonic/fetal growth, which results in inadequate palatel cells for closure. Experimental bioassay data examining the prevalence of cleft palate in mice exposed to the herbicide 2,4,5‐T are used to illustrate the process. With the limited data available, it is necessary to assume a model for cell growth and the relationship between the cell growth rate parameter and dose of 2,4,5‐T. Also, a relationship between cleft palate prevalence and growth is assumed and then checked with experimental data. The purpose for the paper is not to provide a universal biologically based dose–response model for cleft palate, but rather to demonstrate the extent, and type of information and data required. It remains to be seen if the form of the model is appropriate for chemicals that primarily produce embryo/fetal malformations or death via reduced or delayed cellular growth. © 1992 Wiley‐Liss, Inc.
Neural tube defects without neural crest defects in Splotch mice
Authors: Franz Thomas
Published: June 2005

Homozygous Splotch mutant mice (Sp/Sp) die on day 14 of gestation with neural tube defects, curly tail, and malformations of neural crest derivatives. Sp1H mice, which have a radiation‐induced allele of Splotch with a similar phenotype, were used for this study. The neural tube defects are always located in the lumbosacral region and in 50% of the cases also in the region of the hindbrain. In this report, rare cases of neural tube defects and tail defects among the offspring of crosses between Splotch (Sp1H) heterozygotes are presented, which are not associated with a neural crest defect. This suggests that the development of the neural tube and neural crest defects in this mutant is caused by independent mechanisms or is dependent on the dosage of the mutant gene, with different thresholds being pathogenetic in the neural tube and neural crest, respectively. © 1992 Wiley‐Liss, Inc.
Craniometric measurements of craniofacial malformations in the X‐linked hypophosphatemic (Hyp) mouse on two different genetic backgrounds: C57BL/6J and B6C3H
Authors: Gonzalez Cesar D. , Meyer Ralph A. , Iorio Robert J.
Published: June 2005

This study reports data on craniometric measurements in the X‐linked hypophosphatemic (Hyp) mouse on two different genetic backgrounds: C57BL/6J and B6C3H. Heads of normal females “+/+,” normal males “+/Y,” heterozygous mutant females “Hyp/+,” and hemizygous mutant males “Hyp/Y” for each genetic background were examined. Data were collected via skull measurements. On a C57BL/6J background, the neurocranium of mutants “Hyp/+” and “Hyp/Y” was shorter and slightly higher than in normal counterparts. On a B6C3H background, mutant mice “Hyp/+” and “Hyp/Y” were shorter in neurocranial length than in normal counterparts. Viscerocranial height was larger in “Hyp/Y” than in normal counterparts. No differences in neurocranial and mandibular height were found. Mutant mice on a C57BL/6J background were compared to mutant mice on a B6C3H background. No differences in neurocranial length were found. Cranial length was shorter in “Hyp/Y” on C57BL/6J than in “Hyp/+” on B6C3H. Facial length parameters were shorter in “Hyp/Y” on C57BL/6J than in “Hyp/Y” and “Hyp/+” mutant mice on B6C3H. Mandibular length was shorter in “Hyp/Y” on C57BL/6J than in “Hyp/+” on C57BL/6J and both mutant mice (“Hyp/Y” and “Hyp/+”) on a B6C3H background. The results of this study indicate that craniofacial growth is less affected in mutant mice on a B6C3H genetic background than in mutant mice on a C57BL/6J genetic background. © 1992 Wiley‐Liss, Inc.
Nitrofen‐induced congenital diaphragmatic defects in CD1 mice
Authors: Wickman Debra S. , Siebert Joseph R. , Benjamin Denis R.
Published: June 2005

In previous clinical reports, we have documented the association of several morphologic changes with congenital diaphragmatic hernia or, perhaps more appropriately termed, congenital diaphragmatic defect (CDD). These anomalies include decreased cardiac mass with left ventricular hypoplasia in infants with left‐sided CDDs (Siebert et al., '84), enlarged, asymmetric chests (Siebert and Benjamin, '87), and extrathoracic anomalies (Benjamin et al., '88), including urinary tract anomalies and elevated kidney weights in otherwise normal kidneys (Glick et al., '90; Siebert et al., '90). Hypoplastic lungs and hearts and enlarged chests are thought to result from the herniation of abdominal viscera into the thoracic cavity, but for the renal abnormalities, pathogenesis is unclear. The findings are intriguing, for they could mirror unrecognized developmental relationships between the diaphragm, lung, heart, and kidney. In order to further examine these issues and to test the applicability of experimentally produced CDDs to human disease, we administered nitrofen (2,4‐dichlorophenyl‐p‐nitrophenyl ether), an herbicide known to produce diaphragmatic defects in rodents, to time‐mated CD1 mice by gavage feeding on gestational days 8 and 9. Dosages were 200 (low dose) or 500 (high dose) mg/kg body weight, and fetuses were studied on gestational day 18. Diaphragmatic defects occurred in a dose‐response fashion: 0% (0/48) control or sham‐fed, 5% (5/104) in the low‐dose group, and 25% (19/75) in the high‐dose group. Several fetuses with cleft palate, renal agenesis, exencephaly/encephalocele, and/or Di‐George sequence were noted at the high dose, the latter a previously undescribed finding. Diaphragmatic defects were primarily right sided and only associated with herniation of abdominal viscera in animals exposed to 500 mg/kg. Body weight was uniformly decreased and crown‐rump length variably so by nitrofen exposure, while chest diameters were increased. Reduced heart and lung weights and elevated kidney weights were identified in animals exposed to low‐ or high‐dose nitrofen, but this occurred regardless of the presence of a diaphragmatic defect, suggesting that growth of the lung, heart, and kidney is directly affected by nitrofen. Because the effects of nitrofen could not be differentiated from those associated with CDDs or visceral herniation, it is impossible to resolve questions regarding the interrelationships of diaphragmatic defects and pulmonary, renal, and cardiac changes. Morphogenetic, anatomic, and other differences between laboratory rodents and humans reaffirm the need for careful extrapolation between experimental, teratogenic models and human disease. © 1993 Wiley‐Liss, Inc.
Evaluation of congenital limb reduction defects in upstate New York
Authors: Lin Shao , Marshall Elizabeth G. , Davidson Georgia K. , Roth Geraldine B. , Druschel Charlotte M.
Published: June 2005

Limb reduction defects (LRD), reported to the Congenital Malformations Registry in upstate New York between 1983–1987, were invetigated in terms of LRD classification, parental demographics, and LRD characteristics. After excluding LRD with chromosome abnormalities, we followed guidelines developed by the European Congenital Anomaly Surveillance Consortium (EUROCAT) to classify 271 LRD into six groups based on similar patterns of embryological failure. The descriptive analysis indicated a prevalence of 0.45 per 1,000 births (stable over 5 years) for LRD diagnosed during the first 2 years of life. Among 271 LRD cases, 95 were classified as terminal transverse (35.1%), 71 as split limbs (26.2%), 36 as preaxial (13.3%), 32 as postaxial (11.8%), 26 as intercalary (9.6%), and 11 as multiple types (4.1%). In cases with multiple limb involvement (28.4%), two thirds had the same type of LRD in each limb. The multiple types and preaxial groups showed the most distinctive characteristics: they had the highest frequency of suspected syndromes, other birth defects, and syndactyly compared to the other LRD. There were no significant differences in the distribution of demographic variables among different LRD types. Consideration of the incidence and characteristics of LRD by classifying them into these distinct subgroups may be useful for evaluating possible mechanisms of malformation. © 1993 Wiley‐Liss, Inc.
Additional endpoints and overview of a mouse skeletal variant assay for detecting exposure to teratogens
Authors: Beck Sidney L.
Published: June 2005

CD‐1 mice were exposed in utero to one of 14 treatment regimes, several of them being replicated, with close agreement between series. Prenatal exposure to a teratogenic dose at a sensitive time enabled detection of 10 of 14 teratogen regimes by alterations in frequency or severity of a substantial number of the 88 variants in the Skeletal Variant Assay System (SVAS) screen when examined at 60–65 days post natal (DPN). These included 2,4,5‐T (245T), Trifluralin (TFL), Maneb (MNB), Decamethrin (DMT), Acetazolamide (ACZM) either at 8 days post‐coitus (DPC) or days 9–11 PC, trypan blue (TB), or 5′ Bromodeoxyuridine (BUDR) on either 7 DPC, 8 DPC, or 9 DPC. Most of these observations have been reported elsewhere.

All of the treatment regimes mentioned above, and another group of treatments, could be detected in the exposed CD‐1 cohorts when additional endpoints were employed. One such endpoint was “frequently responding variants.” These were: Interfrontals (IF), Parted Frontals (PF), Preoptic Sutures (PS), Foramina Transversaria Imperfecta of the first cervical (C) vertebra (FTI C1), FTI of the axis (C2), Accessory (Acc) Transverse Foramina (TF) of C3–C6, malformations of C3–C7, Fourteen (14) Ribs, Carpal Fusions (Fus), Lumbar Fus, 27‐Presacral Vertebrae (PSV), and Sacral Fus. This endpoint revealed significant differences in the initial group of 10, plus Captan (CAPT) and Phenytoin (DPH). Yet another useful endpoint reported here was the existence of high magnitude effects (i.e., dramatic alterations in frequency of occurrence of a variant). These included IF in TB and ACZM; PF in ACZM; PS in BUDR; FTI‐C1 in TB and 245T; FTI‐C2 in 245T; 14 Ribs in ACZM, BUDR, and TFL; Carpal Fus in TB; 27‐PSV in ACZM; Fewer than (<) 30 Caudal Vertebrae (Vert) in 245T, TFL; Caudal Fus in TB, ACZM‐D9. Eight treatment regimes in all could be detected by the existence of 3 or more high magnitude effects (245T, MNB, TB, ACZM8, ACZM9‐11, phenytoin, and possibly BUDR on days 7 or 8, each seen in one of two series only).

Clusters of related variants were affected in 9 of the 14 groups: Frontal (F) bones and C Vert in 245T; F bones in ACZM‐D8; Fus in Posterior Vert Column in ACZM‐D9‐11; C Vert and Fus in Vert and articular skeleton in TB; Thoracic (Th) Vert and rib‐cage effects in BUDR. Finally, unique effects were seen in 4 of the 14 groups: Fused F and F Foramen (For) variants in 245T; For Palatinum Minus Posterior Double in TFL; Maxillary For I Absent (Abs), Dyssymphysis/Fus Th Vert, Tarsal Fus, the magnitude of the IF effect in TB; Acc Mental For in ACZM.

Using one or more of the endpoints employed, 12 of the teratogenic regimes employed (not cortisone or thalidomide exposure) could be detected in the surviving, non‐malformed adult CD‐1 populations; 9 of the 12 were positive for three or more of the five endpoints. © 1993 Wiley‐Liss, Inc.
Embryonic development in vitro following short‐duration exposure to heat
Authors: Kimmel G. L. , Cuff J. M. , Kimmel C. A. , Heredia D. J. , Tudor N. , Silverman P. M.
Published: June 2005

Gestation day (GD) 10 rat embryos (10–12 somites) were exposed in vitro for 10 to 25 minutes at 42 or 43°C and evaluated 24 hrs later for alterations in growth and specific morphological parameters, using a modified Brown‐Fabro (Brown and Fabro: Teratology, 24:65–78, '81) scoring system that allowed evaluation of development relative to gestational age. At 42°C, crownrump length appeared to be particularly sensitive, responding to only 10 mins exposure. A 15‐min exposure resulted in decreased total protein, somite number and morphological score. No system was uniquely sensitive, since all parameters demonstrated some degree of response. Rather, systems affected were those that would be developing most rapidly at this time in gestation. At 43°C, all of the parameters measured were affected by a 10‐min exposure. These results demonstrate alterations in vitro after much shorter exposure periods than previously reported on GD10, which may be due, in part, to the use of a modified scoring system that permitted the evaluation of graded individual end point changes relative to gestational age. The response patterns demonstrated a clear temperature‐ and exposure duration‐dependency, with a shift from a more shallow duration‐response curve to a more dramatic inhibition of development as temperature increased from 42°C to 43°C. © 1993 Wiley‐Liss, Inc.
Statistical model for fetal death, fetal weight, and malformation in developmental toxicity studies
Authors: Catalano Paul J. , Scharfstein Daniel O. , Ryan Louise M. , Kimmel Carole A. , Kimmel Gary L.
Published: June 2005

The purpose of this paper is to present a statistical model for analyzing the joint effects of exposure on fetal death, fetal weight, and malformation in a developmental toxicity study. In addition to allowing for the usual litter effect, the model allows for correlations between different outcomes measured on the same fetus. Fitting the model requires first focusing on non‐live outcomes by modeling the probability of fetal death or resorption as a function of dose. Then outcomes among live fetuses are modeled using a two‐stage regression approach. The first stage models fetal weight as a function of dose and the second stage models fetal malformation as a function of dose, as well as residuals from the weight model. The regression coefficients from the malformation model have intuitive interpretations in terms of correlations between littermates and between different outcomes measured within the same fetus. Not only does the approach provide a useful way to investigate the relationship between adverse fetal outcomes, it also yields a natural framework for conducting quantitative risk assessment. A procedure is proposed for quantifying overall risk by incorporating the three outcomes in order to estimate safe dose levels and corresponding lower confidence limits. The method is illustrated using data from an experiment in mice conducted through the National Toxicology Program. © 1993 Wiley‐Liss, Inc.
Mouse placenta: Hemodynamics in the main maternal vessel and histopathologic changes induced by 2‐methoxyethanol and 2‐methoxyacetic acid following maternal dosing
Authors: Khera K. S.
Published: June 2005

The two main maternal vessels that are a major, if not the entire, source of maternal blood for the mouse placenta are unique in possessing intraluminal valvular projections. The morphologic configuration of these projections suggests their potential to converge, diverge, and rotate blood currents flowing under systolic pressure. The intravascular occurrence of circular fibrin bodies composed of concentric fibrin strands coagulated from the plasma and almost no blood cellular elements in these strands lends credence to this concept. Histopathologic changes in the extraembryonic and embryonic tissues induced by an intraperitoneal injection of 250 or 500 mg/kg of 2‐methoxyethanol, or its metabolite, 2‐methoxyacetic acid, via oral gavage were determined 48 hr after dosing CD‐1 mice on day 11 of pregnancy. Both compounds caused 1) marked congestion and dilatation, associated with or without fibrinous occlusions, of the main maternal vessel of the placenta, 2) serosanguinous exudation and maternal hemorrhages from the placental periphery, 3) necrosis and desquamation involving the mesometrial surface or peripheral edge of the placenta, 4) translabyrinthine embryonic hemorrhage into the maternal circulation, and 5) embryonic hemorrhages into the exocoelomic, amniotic, and pericardial cavities. These lesions signify a disordered maternal circulation in the placenta suggestive of potentially serious pathologic effects. These lesions may play a role in the resorption, reduction in fetal body weight, and syndactyly or oligodactyly attributed to 2‐methoxyethanol and 2‐methoxyacetic acid. © 1993 Wiley‐Liss, Inc.
Genetic analysis of the maternal factors controlling the survival of trisomy 16 mouse fetuses
Authors: Demczuk Suzanne , Vekemans Michel
Published: June 2005

The B × H recombinant inbred strains of mice were used to undertake a genetic analysis of the maternal factors controlling the survival of trisomy 16 fetuses. The data presented indicate that the prevalence of trisomic fetuses on day 15 of gestation varies significantly with the genetic background of the mother. The strain difference in the frequency of trisomy appears to be the result of selective elimination of trisomic fetuses. Various statistical methods employed to elucidate the genetic architecture of the trait from the recombinant inbred strains data indicate that the number of loci involved in the selection process ranges from one to five. Linkage association with two loci has been found; however, with a low probability level (P= 0.292). © 1993 Wiley‐Liss, Inc.
Microsurgical study on the mechanisms determining sidedness of axial rotation in rat embryos
Authors: Fujinaga Masahiko , Baden Jeffrey M.
Published: June 2005

Sidedness of left/right asymmetric body structures is strongly biased in most animals by mechanisms that are not well understood. In rat embryos, axial rotation starts at the 9–10 somite stage and is almost completed at the 17–18 somite stage. As a result, the ventrally flexed tail (caudal part of the body) and chorioallantoic placenta on the yolk sac take up their position normally on the right side of the embryo. Because the tail and chorion become connected via the allantois around the time when axial rotation takes place, we hypothesized that the allantois and possibly its connection to the chorion is important in determining sidedness of the tail. In the present study, we tested this hypothesis by surgically removing either the allantois or chorion before axial rotation started. Embryos were explanted at 8 am on Day 9 of gestation (presomite stage), and either the allantois or chorion was removed using microforceps. Embryos were then cultured in rotating bottles, and sidedness of the tail, chorioallantoic placenta, and bulboventricular loop (heart) was determined after 50 hours (∼25–26 somite stage). Removal of the allantois (n = 55) resulted in absence of the umbilical cord and a 49.1% incidence of inverted tail; a chorioallantoic placenta‐like structure developed on the yolk sac in the normal position. Removal of the chorion (n = 114) resulted in absence of the chorioallantoic placenta and a 20.2% incidence of inverted tail; the allantois either floated in the extraembryonic coelomic cavity or reached the yolk sac but did not form a chorioallantoic placenta‐like structure. Sidedness of the heart was not affected in either group. These results indicate that removal of the allantois results in complete loss of control of tail sidedness, whereas removal of the chorion results in only a partial loss of control. An incidental finding was that an avascular area developed on the yolk sac around the chorioallantoic placenta. This area became larger when the allantois was removed but disappeared when the chorion was removed. © 1993 Wiley‐Liss, Inc.
Hydantoin syndrome with holoprosencephaly: A possible rare teratogenic effect
Authors: Kotzot Dieter , Weigl Josef , Huk Walter , Rott Hans‐Dieter
Published: June 2005

We report on a newborn girl with lobar holoprosencephaly and clinical signs of hydantoin syndrome. During pregnancy the mother was treated with diphenylhydantoin and primidon for psychomotor and petit mal seizures. The possible relationship between hydantoin syndrome, holoprosencephaly, and maternal intake of anticonvulsants during pregnancy is discussed. © 1993 Wiley‐Liss, Inc.
Potentiation of triamcinolone‐induced cleft palate in mice by maternal high dietary fat
Authors: Zhou Mian , Walker Bruce E.
Published: June 2005

This study investigated whether the current range in dietary fat levels, which has arisen partly in response to some major health concerns, would affect frequency of congenital anomalies if continued into the period of early pregnancy. The effect of 5.6%, or 48% of calories from fat in the maternal diet, was tested on pregnant strain CD‐1 mice injected with triamcinolone in doses of 0.01 mg, 0.02 mg, 0.04 mg, or 0.06 mg per day on days 11 through 14 of gestation. Frequency of cleft palate increased with increasing doses of triamcinolone, with clefts of the palate being rare at the two lower doses. No clefts appeared without triamcinolone on either diet. In combination with triamcinolone treatment, 226 fetuses exposed to a maternal low fat diet had normal palates and 86 had cleft palates. With exposure to high fat, 186 fetuses had normal palates and 101 had cleft palates, which was a significant increase in clefting (p < 0.05). Also, the latter group showed a greater degree of retardation in palate development (p < 0.05). Thus both a greater frequency and a more severe form of clefting support the conclusion that high dietary fat potentiated the cleft palate‐producing effects of triamcinolone in mice. © 1993 Wiley‐Liss, Inc.
Utility of the murine erythroleukemic cell (MELC) in assessing mechanisms of action of DNA‐active developmental toxicants: Application to 5‐fluorouracil
Authors: Elstein Kenneth H. , Zucker Robert M. , Shuey Dana L. , Lau Christopher , Chernoff Neil , Rogers John M.
Published: June 2005

Murine erythroleukemic cells (MELC) exposed to 2′‐deoxy‐5‐azacytidine (D‐AZA) or to the active cyclophosphamide (CP) metabolites phosphoramide mustard (PAM) and 4‐hydroxycyclophosphamide (OHCP) exhibit cell‐cycle perturbations similar to those seen in limb bud nuclei of gestational day (GD) 10 CD‐1 mouse embryos exposed in utero to D‐AZA or CP, respectively. The similarities in response suggest MELC may be a useful model for determining mechanisms of action of DNA‐active developmental toxicants. As such, we used the MELC model to investigate the mechanism of action of 5‐fluorouracil (5‐FU), an antimetabolite that induced in GD 14 rat fetuses an apparent S‐phase accumulation in limb cells 8 hr after in utero exposure, but S‐phase depletion in liver cells 24 hr postexposure. MELC timed‐recovery and synchronization studies suggest that in proliferative tissues, 5‐FU induces an early S‐phase accumulation, followed by a synchronous, concentration‐dependent delay in progression through the cell cycle. Consequently, it is the tissuespecific rate of delay, rather than different mechanisms of action, that results in apparent tissue‐specific perturbations. Moreover, growth and cell‐cycle data suggest that cells entering S phase (when TS activity is greatest) are the most sensitive to 5‐FU toxicity. Assays of the TS activity of recovering MELC reveal that although the initial extent of TS inhibition does not appear to be concentration‐dependent, the time to recovery is, suggesting that the rate of S‐phase progression is closely associated with TS activity. Together, the induction of similar cell‐cycle perturbations in embryonic/fetal tissues and MELC following exposure to CP (or CP metabolites), D‐AZA, or 5‐FU, as well as the adaptability of MELC to a variety of kinetic assays suggests that, for those developmental toxicants suspected of inducing cell‐cycle perturbations in embryonic/fetal tissues, MELC may prove useful for elucidating mechanisms of action. © 1993 Wiley‐Liss, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.