Comparative teratogenic activities of two retinoids: effects on palate and limb development

Two closely related retinoids, all-trans and 13-cis retinoic acids, were assessed for their relative activities as teratogens in ICR mice by monitoring the frequency with which either isomer produced discrete dysmorphogenesis of the embryonic limb and the secondary palate. A single oral dose of all-trans retinoic acid at 100 mg/kg on either day 11.5 or 12.0 of gestation (plug day = day one) was maximally effective; more than 90% of the treated embryos developed reduction defects of the limb bones and an equally high percentage also had cleft palate. The limb development was most sensitive on day 11.5 of gestation while the peak susceptibility for palatal clefts began on day 12.0. Under identical experimental conditions, treatment with 100 mg/kg 13-cis retinoic acid produced no apparent teratogenic effects. By assessing the relative incidence of readily identifiable malformations of the limb and palate associated with various doses of the two isomers, we found that 13-cis retinoic acid was four to eight times less embryopathic than all-trans retinoic acid. Since the mechanism of teratogenic action of retinoids is still far from clear, it is suggested that further studies on causative factors will be greatly assisted by the use of these two closely related retinoids, which substantially differ from each other in their teratogenic potency.     

Comparative teratogenicity of triamcinolone acetonide, triamcinolone, and cortisol in the rat

Pregnant rats were injected im with 0.5 mg/kg triamcinolone acetonide (TAC) on day 12, 13, or 14 of gestation and the fetuses were examined for cleft palate on day 20. All three TAC-treated groups showed an increased proportion of fetuses with cleft palate compared to an untreated control group. Only the group treated on day 13 showed a significant increase in the proportion of litters affected. This indicates that day 13 of gestation is the most sensitive day for cleft palate induction by TAC in the rat. Pregnant rats were then treated on day 13 of gestation with either TAC, triamcinolone (TA), or cortisol. TAC was 59 times as potent as TA in inducing cleft palate, with ED50 values of 1.1 mg/kg and 65 mg/kg respectively. Cortisol induced a significant increase in cleft palates at 500 mg/kg, but the efficacy of this compound was too low to calculate an ED50 and relative teratogenic potency value. Other developmental abnormalities including umbilical hernias, resorption, and fetal death resulted from TAC treatment. Fetal growth retardation was produced by all three compounds. The rank order of teratogenic potency was determined to be TAC greater than TA greater than cortisol.     

Craniofacial abnormalities induced by retinoic acid: a preliminary histological and scanning electron microscopic (SEM) study.

Exogenous retinoic acid has been found to be teratogenic in animals and man. Craniofacial defects induced by retinoic acid have stimulated considerable research interest. The present report deals with scanning electron microscopical observations of the craniofacial region concurrent with histological examination of craniofacial dysmorphism induced in rat embryos following maternal treatment treated with varying dosages of all-trans-retinoic acid (tretinoin). Two groups of pregnant rats were treated with rat embryos exposed to retinoic acid suspended in corn oil (100 mg/kg b.w. on gestational day 11.5 and 50 mg/kg b.w. on gestational day 10, 11 and 12 respectively). A third group was treated with corn oil (vehicle) while a fourth group remained untreated. A wide spectrum of congenital abnormalities, including exophthalmos, microphthalmia and anophthalmia, maxillo-mandibular dysostosis, micrognathia of both maxilla and mandible, cleft palate, subdevelopment of ear lobe, preauricular tags and macroglossia, were observed in the offspring of retinoic acid treated animals. The abnormalities were both time and dosage dependent, and characteristic of Treacher Collins syndrome when retinoic-acid was administered on gestational day 11.5. In contrast, when retinoic acid was administered were on gestational days 10-12, the defects were similar to those seen in the first and second pharyngeal arch syndrome, as well as in the oculo-auriculo-vertebral spectrum. Whereas our data support the hypothesis that all-trans retinoic-acid disturbs growth and differentiation of several embryonic cell types essential for normal craniofacial development, its mechanism of action remains unclear.     

Differential expression of decorin and biglycan genes during palatogenesis in normal and retinoic acid-treated mice.

Proteoglycans are involved in secondary palate formation. In the present study, we focused on two small leucine-rich proteoglycans, decorin and biglycan, because they assembled extracellular matrix molecules such as collagens and modulated signaling pathway of transforming growth factor-beta. To investigate the functions of decorin and biglycan in palatogenesis, we compared their mRNA expression patterns between normal palate and retinoic acid-induced cleft palate in mice by using in situ hybridization analysis during the period of embryonic day 13.5 (E13.5) to E15.5. On E13.5, decorin mRNA was expressed in the epithelia and mesenchyme on the nasal side of the developing secondary palate. During the period the palate shelves were fusing (E14.5), decorin mRNA was strongly expressed in the mesenchyme but its expression pattern was asymmetric; decorin mRNA expression area in the nasal side was broader than that in the oral side. The expression of decorin mRNA was hardly detected in the mesenchyme on either side of the medial edge epithelium. After fusion (E15.5), its expression converged to the mesenchyme just around the palatine bone. Biglycan mRNA was ubiquitously distributed throughout the palatal mesenchyme for the mid-gestation period. Its expression area became limited to the ossification area within the palate after the late gestation period. In the retinoic acid-treated mice, the area of the decorin gene expression expanded to the core region of the palate primordium where little signal was observed in control mice. On the other hand, biglycan in the retinoic acid-treated mice did not show remarkable change in its distribution patterns compared with that in the control mice. These findings suggest that decorin and biglycan play distinct roles in palatogenesis, and decorin was more actively involved in the process of secondary palate formation than biglycan. Up-regulation of decorin gene expression in the retinoic acid-treated mice might influence the pathogenesis of cleft palate.     

The effects of cyclophosphamide, melatonin and carvedilol on neural tube and skeletal system of mice fetuses in prenatal period

Cyclophosphamide (CP) as an alkylating agent is used for treatment of cancer and to prevent rejection of tissue transplantation. There are many reports that the teratogenic effects of cyclophosphamide can be prevented by application of antioxidant drugs and stimulation of the maternal immune system. Also, there is some evidence that melatonin and carvedilol are antioxidant.Therefore, in this study, the prophylactic effects of melatonin and carvedilol on teratogenic effects of CP was compared. This study was performed on 31 pregnant mice that were divided into six groups. The control group received normal saline and test groups received CP (20 mg/kg), carvedilol (5 mg/kg), melatonin (10 mg/kg), CP (20 mg/kg) pluscarvedilol (5 mg/kg) and CP (20 mg/kg) plus melatonin (10 mg/kg) intraperitoneally on the 10th day of gestation, respectively. Fetuses were collected on the 19th day of gestation and after determination of weight and length; they were stained by Alizarin red-Alcian blue method. Cleft palate, spina bifida and exencephalyincidence were 62.79%, 62.79% and 30.23% in fetuses of mice that received only CP. Cleft palate,spina bifida, exencephaly, and incidence were 45.45%, 9.09% and 0% in group which received CP plus carvedilol (5 mg/kg), respectively.However, cleft palate, spina bifida and exencephalyincidence were 62.5%, 45.83% and 4.16% range in the group which received CP plus melatonin (10 mg/kg), respectively. In addition, theincidence of skeletal anomalies including limb, vertebral, and sternaldefects were decreased by melatonin and carvedilol. The mean weight and length of animal fetuses that had received melatonin and carvedilol were significantly greater than those receiving only CP. It is concluded; carvedilol has a significant effect in preventing CP-induced malformations and in cases like CP-induced exencephaly, cleft palate and spina bifidahas better prophylactic effect than melatonin, but this improvement is not significant.     

Indospicine—The Teratogenic Factor from Indigofera spicata Extract Causing cleft Palate

The amidine-containing amino acid, indospicine, has been shown to be the teratogenic principle in the crude Indigofera spicata extract which causes cleft palate in foetal rats exposed to it on Day 13 of gestation. Possible implications of its chemical structure are discussed.     

Potentiation of chemically induced cleft palate by ethanol ingestion during gestation in the mouse

The influence of ethanol consumption on cleft palate induction by methylmercury, cortisone, and retinyl acetate was investigated in Swiss white mice. Consumption of 20% ethanol throughout gestation significantly increased the incidence of cleft palate compared to water-fed mice, when methylmercury was given on four consecutive days (days 9-12, 5 mg/kg of body weight). Ethanol also increased the incidence of cleft palate in mice given retinyl acetate (3,400 or 5,100 IU) on day 12, compared to retinol acetate-treated mice given water, but did not affect cleft palate induction by cortisone (2.5 mg/d, days 8-11). Ethanol significantly reduced fetal weight in the presence or absence of the three teratogens, but the results do not support a hypothesis that growth retardation is directly responsible for the potentiating action of ethanol. It may be that ethanol acts to increase cleft palate induction by some teratogens by retarding fetal developmental processes.     

Histological observations of palatal malformations in rat embryos induced by retinoic acid treatment.

Malformations of the palate were induced in white rat embryos following maternal exposure to retinoic acid (tretinoin). Five experimental groups and the controls were treated by the following protocol: Group 1: pregnant rats received 100 mg retinoic acid (RA)/kg b.w. suspended in corn oil on gestational day (GD) 11.5; Group 2: 20 mg RA/kg b.w. from GD 8-12; Group 3: 20 mg RA/kg b.w. from GD 7.5-11.5; Group 4: 100 mg RA/kg b.w. on GD 10-11; Group 5: 100 mg RA/kg b.w. on GD 10 and 12; Group 6 received corn oil vehicle from GD 7-14.5; and Group 6: served as non-injected controls. In all retinoic acid treated groups, varying degrees of clefts with occasional attempts of fusion were noted. The severity and frequency of the malformations were dependent on dosage or gestational day of drug treatment. Our results indicate that RA, even at the lowest dose tested (20 mg/kg b.w.) severely affects the various tissues constituting the embryonic palatal shelves by altering cell interaction and possibly programmed cell death. These events would then result in lack of or inadequate differentiation with subsequent formation of aberrant craniofacial architecture.     

Effect of valproic acid on fetal and maternal organs in the mouse: a morphological study

Valproic acid (VPA) is an antiepileptic drug used clinically. Because of its known teratogenic properties VPA is not recommended for women of child bearing age. The present study was designed to assess the effects of VPA on both fetal and maternal organs. Randomized groups of pregnant mice were treated as follows: Group 1 (n = 10) 500 mg/kg VPA/day on gestation days 8-11; Group 2 (n = 10) 600 mg/kg VPA/day on gestation days 8-11; and Group 3 (n = 4) saline-injected controls. On gestation day 18, the pregnant mice were euthanized, fetuses collected and prepared for scanning electron microscopy. In addition, fetal and maternal organs were processed for routine histology, immunohistochemistry for growth factors (TGF alpha, beta-1, beta-2 and EGF) and transmission electron microscopy. Scanning microscopy revealed specific lesions induced by VPA in the fetus, namely spina bifida occulta, exencephaly, and exophthalmia. On the other hand, there were no detectable morphological changes in fetal or maternal organs by routine histology, immunohistochemistry or electron microscopy. The data suggest that the lesions present in the fetus are due to a direct effect by VPA on retinoic acid, a ubiquitous compound that has a role in normal development, rather than the lack of transport of sufficient nutrients to the fetus as a result of placental insufficiency due to VPA-induced toxicity.     

Developmental toxicity of dinocap in the mouse is not due to two isomers of the major active ingredients

Technical-grade dinocap, a complex-mixture fungicide, is teratogenic in the CD-1 mouse, causing cleft palate and otolith defects. In this study we compared the developmental toxicities of 2,4-dinitro-6-(1-methylheptyl)phenyl crotonate and 2,6-dinitro-4-(1-methylheptyl)phenyl crotonate, model isomers of the major active ingredients of technical dinocap, to the known teratogenicity of the technical compound. Individual isomers, both isomers combined, or technical dinocap were administered to pregnant mice on days 7-16 of gestation. Some dams were killed at term and litters were removed, dead fetuses and resorptions were counted, and live fetuses were weighed and preserved in Bodian's fixative for examination for cleft palate. Other treated dams were allowed to give birth: postnatal viability and growth, development of swimming behavior, and otolith formation were evaluated. As in previous studies, technical-grade dinocap caused cleft palate and weight deficits in fetuses at term and increased neonatal mortality and abnormal swimming behavior, torticollis, and deficient otolith formation in surviving pups. Neither of the purified isomers exhibited any developmental toxicity when administered under identical conditions. Thus, it is concluded that these isomers are not the active teratogenic component(s) in technical-grade dinocap.     

All trans retinoic acid interfering with palatal development. Scanning electron microscopical and light microscopical observations on embryonic rat palate

Diverse studies on retinoic acid teratogenesis, during the recent years, indicate that the drug's analogues target on diverse cell population during differentiation in mammals. During an extended teratological protocol concerning retinoic acid influence in diverse embryonic tissue differentiation in experimental animals we studied all-trans-retinoic acid's influence on palatal development in the white rat embryo. For this purpose, six groups of white rat embryos were studied: Group 1 was treated with 100 mg/kilogram of body weight (k.b.w.) on gestational days (g.d.) 10th and 11th, Group 2 was treated with 100 mg all-trans-retinoic acid/k.b.w. on g.d. 11.5, Group 3 was treated with 50 mg all-trans retinoic acid/k.b.w. on g.d. 10th, 11th and 12th, Group 4 was treated with 50 mg all-trans-retinoic acid/k.b.w. on g.d. 11th and 12th, Group 5 was treated with 20 mg all-trans-retinoic acid/k.b.w. on g.d. 7.5, 8.5, 9.5, 10.5 and 11.5, Group 6 remained untreated. Embryonic heads aged 20 days were observed by light microscopy and scanning electron microscopy. In all treated groups clefts and malformations concerning the differentiation of palatal cell populations were observed. All our findings were compared with normal palatal morphology of untreated "control" embryos. Among the malformations, median clefts were observed, extended along only a part of the primary and all the secondary palate for group 2, the primary and secondary palate for groups 1, 3 and 5 while on group 4, an irregularity of the median palatal raphe and rugae were combined with a median incomplete cleft extended between the primary and secondary palate. Our results are discussed in relation with the international literature results.     

Prevalence of duplications and deletions of the 22q11 DiGeorge syndrome region in a population-based sample of infants with cleft palate

The prevalence of duplications and deletions of the 22q11.2 (DiGeorge syndrome) region was studied among babies born in Norway with open cleft palate without cleft lip (cleft palate only, CPO). During a 5-year period (1996-2001), there were 245 live births with CPO that were referred for surgery. DNA was available from 174 cases with overt cleft palate. DNA copy number was analyzed with the multiplex ligation-dependent probe amplification (MLPA) technique, and an unambiguous result was obtained in 169 (97%) of the samples. We found no 22q11.2 duplications, and one known, and two previously undiagnosed cases with 22q11.2 deletions. All three del22q11-syndrome cases also had heart malformations, which represent one-third of the 10 babies with heart malformations in our study population. The prevalence of del22q11-syndrome among babies with cleft palate with or without additional malformations was 1 of 57 (1.8%). Because the prevalence of CPO in the 35 22q11.2 duplication cases published was 20%, we also investigated if dup22q11-testing was warranted in this group. However, no 22q11.2 duplications were found, indicating that the duplication cases ascertained so far might not be representative of the dup22q11-group as a whole. We conclude that neither del22q11 nor dup22q11 testing is warranted in babies with overt cleft palate as the only finding.     

Cleft palate susceptibility maps in two H-2 subregions, H-2K to I-B and G to H-2D

Data presented here defines the map of H-2 associated genes which affect the glucocorticoid-induced cleft palate frequency to the regions H-2K to I-B and G to H-2D. This was done by observing in four congenic strains the frequency of cleft palate induced by 160 mg/kg of dexamethasone administered to pregnant females on day 12 of gestation. The strains used were B10.A/Sg.Sn, C57BL/10Sn, B10.A (5R)/SgSn and B10.A(18R)/Sg. Additionally the cleft palate frequency was observed in a large number of litters from saline-treated pregnant females. The cleft palate frequency in this control was very low and the rank of strains was the same as for the glucocorticoid-induced cleft-palate frequency. This observation suggests that the induced cleft palate frequency reflects the spontaneous occurrence of isolated cleft palate in these strains.     

Teratogenicity and embryotoxicity of nickel carbonyl in Syrian hamsters

Nickel carbonyl was administered to groups of pregnant hamsters by inhalation (0.06 mg Ni(CO)4/liter/15 min) on days 4, 5, 6, 7, or 8 of gestation. The dams were killed on day 15 of gestation, and the fetuses were examined for malformations. Exposure to Ni(CO)4 on days 4 or 5 of gestation resulted in malformations in 5.5% (8/146) and 5.8% (10/171) of the progeny, respectively (P less than 0.05, versus 0/95 in controls). The proportions of litters with malformed fetuses were 33% (4/12) and 24% (4/17) in dams exposed to Ni(CO)4 on days 4 and 5 of gestation (P less than 0.05, versus 0/9 in litters of control dams). Progeny of dams exposed to Ni(CO)4 on days 4 and 5 included 9 fetuses with cystic lungs, 7 fetuses with exencephaly, 1 fetus with exencephaly plus fused rib, and 1 fetus with anophthalmia plus cleft palate. Hemorrhages into serous cavities were found in 18% (26/146) and 25% (42/171) of fetuses of dams exposed to Ni(CO)4 on days 4 or 5 of gestation. Such hemorrhages were not observed in controls. In progeny of dams exposed to Ni(CO)4 on days 6 or 7 of gestation, there was 1 fetus with fused ribs and there were 2 fetuses with hydronephrosis. In another experiment, pregnant hamsters were exposed to inhalation of Ni(CO)4 (0.06 mg/liter/15 min) on day 5 of gestation; these dams were permitted to deliver their litters and to nurse their pups. On the day of delivery, there was no significant difference in the average number of live pups in the Ni(CO)4-exposed litters compared to control litters. Neonatal mortality was increased in Ni(CO)4-exposed litters; by day 4 postpartum, the number of live pups averaged 7.6 +/- 1.5 in Ni(CO)4-exposed litters (P less than 0.01 versus 9.6 +/- 1.8 pups in control litters). This study demonstrates that Ni(CO)4 is teratogenic and embryotoxic in Syrian hamsters.     

Pierre Robin sequence associated with first trimester fetal tamoxifen exposure

Tamoxifen is a nonsteroidal antiestrogen used as the current adjuvant endocrine treatment of choice for premenopausal women treated for breast cancer and its potential for causing fetal harm during pregnancy remains inconclusive. While the evidence of tamoxifen's effects on humans in utero is minimal, animal studies have shown evidence of teratogenicity, hence the FDA's class D categorization of the drug. In 1994 Cullins et al. published a case report entitled "Goldenhar's Syndrome Associated with Tamoxifen Given to the Mother During Gestation." At the time of publication, the authors noted that the manufacturer of tamoxifen knew of two cases associated with tamoxifen administration which resulted in congenital craniofacial defects. Cullins' case of Goldenhar syndrome is also a craniofacial disorder and thus represented the third such case. We report on the fourth case of a tamoxifen-associated craniofacial anomaly. The mother became pregnant while undergoing tamoxifen therapy for breast cancer. A child with severe micrognathia and cleft palate was born. It is noteworthy that the two patterns of craniofacial malformations in tamoxifen exposed infants--Goldenhar syndrome in Cullins' et al. case and Pierre Robin sequence reported here--have also both been observed in isotretinoin exposed infants. While a larger spectrum of anomalies is characteristic of retinoic acid embryopathy, the specific craniofacial anomalies include facial asymmetry, microtia, micrognatha and U-shaped cleft of the secondary palate, that is, malformations seen in the two tamoxifen exposed infants. Therefore, it is conceivable that these two agents could produce comparable embryotoxic effects if they function in a like way during embryogenesis. While the majority of tamoxifen exposed infants are normal, the ascertainment of teratogenic effects from tamoxifen will best be determined by data from teratogen registries.     

Transplacental teratogenesis and mutagenesis in mouse fetuses treated with cyclophosphamide

We studied transplacental fetotoxicity, teratogenicity, and mutagenicity in Swiss Webster mice following different doses of cyclophosphamide (CP; 0, 5, 10, 15, or 20 mg/kg), a well-known mutagen/teratogen, on day 12 of gestation. The fetal survival and weight on day 18 of gestation decreased significantly with increasing CP dose (P less than 0.01). The CP-treated fetuses were also dysmorphic (e.g., shortened limbs, digital defects, cleft palate, open eyes, and hydrocephaly) and the percentage of dysmorphology increased with increasing CP doses (P less than 0.01). To evaluate mutagenesis, a separate group of females received 5-bromodeoxyuridine tablet (50-mg) implants on day 12 of gestation and a CP treatment 8 h later. Fetal liver cells were harvested 24 h post-BrdU implant to analyze sister chromatid exchange (SCE) frequency and micronuclei. CP caused a significant increase in the SCEs per fetal liver cell from 3.4 +/- 0.02 (control) to 90.0 +/- 0.04 (20 mg/kg CP) (P less than 0.01). The increasing CP dose was also related to an increase in micronuclei. The data suggest that CP is transplacentally toxic, teratogenic, and mutagenic. Further analyses of the data suggest that the mutagenic effects of CP may in fact contribute indirectly to the CP-related teratogenic effects. Such conclusions are based on path analysis with directional causations associated with SCEs per cell and the dysmorphic features studied.     

腭裂小鼠牙胚发育中β-连环蛋白的表达

背景：牙齿发育生物学中信号传导是热点问题,β-连环蛋白是Wnt信号传导通路中的关键效应因子,其在发育的牙胚中有普遍表达,并且在内釉上皮、釉结、星网状层、中间层的表达有时空变化。 目的：通过苏木精-伊红染色和免疫组化技术,观察牙胚在维甲酸诱导腭裂发生中的形态学变化及β-连环蛋白的表达变化。 方法：选取C57BL/6J近交系小鼠,按雌雄比2∶1于晚8时合笼,次日8时检查雌鼠,发现阴栓视为妊娠,定为E0 d。18只孕鼠随机分为3组：在E10 d,实验组以维甲酸100 mg/kg对孕鼠行一次性灌胃,制备腭裂动物模型;植物油对照组给予10 mL/kg橄榄油灌胃;空白对照组不做任何处理。 结果与结论：β-连环蛋白在空白对照组E13 d牙胚蕾状期、E14 d帽状期、E16 d钟状期上皮内均有表达,且空白对照组的表达随着牙胚发育的成熟而逐渐增加,实验组的变化趋势与空白对照组相同。3个时期的实验组β-连环蛋白在牙胚中的表达水平均高于空白对照组,植物油对照组和空白对照组表达无明显差异。提示维甲酸在诱导腭裂发生过程中,可能通过干扰上皮-间充质间的相互作用,上调β-连环蛋白在牙胚中的表达,使牙胚发育受阻。     

Teratogenic profile of retinylidene methyl nitrone and retinol in Swiss-Webster mice

A single oral dose of 75 mg/kg of all-trans-retinol or all-trans-retinylidene methyl nitrone, retinoids with potential cancer chemopreventive properties, on one of five successive days of embryogenesis resulted in a shift in the pattern of developmental anomalies in fetal mice. Treatment on days 7, 8, or 9 with retinal primarily induced malformations of the head whereas treatment on day 11 induced bilateral forelimb reduction defects. Treatment on day 8 with either retinoid produced the highest in utero death rate. Intubation of either retinoid on day 10 failed to induce a significant increase in the number of litters containing offspring with malformations, and the embryonic death rate declined to control values. The malformations induced by administration of either retinoid were similar, but retinol was always associated with a higher total percentage of malformed offspring. The similar teratogenic profile of these two retinoids may be related to their in vivo biotransformation to all-trans-retinoic acid.     

Sex-related differences in procarbazine-induced cleft palate and microgenia and the anti-teratogenic effect of prenatal folic acid supplementation in rats.

Sex-related differences in the frequency of cleft palates and microgenia in rat fetuses prenatally treated with procarbazine (200 mg/kg on day 14 of gestation (GD14), group 1), and the anti-teratogenic effect of prenatal folic acid supplementation (4 mg/kg on GD14 through GD17, group 2) were studied in LEW.1A rats. In group 1, complete clefts were observed in 69% of the male and in 36% of the female fetuses while incomplete clefts (present only in the hard palate) were exhibited by 31% of the males and 43% of the females. Microgenia occurred in all males but only in 64% of the female fetuses. In group 2, the prenatal folic acid supplementation significantly reduced the occurrence frequency of complete clefts to 9% in males and to 0% in females. In contrast, incomplete clefts increased to 82% in males and 91% in females. Microgenias were reduced to 73% and 57% in male and female fetuses, respectively. Since incomplete clefts present in the hard palate are assumed to be residues of spontaneous intra-uterine repair processes of exogenously induced complete palatal clefts, we conclude that prenatal supplementation with folic acid at a dose of 4 mg/kg promotes the intra-uterine repair of cleft palates and offers a partial protection against procarbazine teratogenicity. Furthermore, it is deduced that gender-specific differences exist in the susceptibility to procarbazine and in the anti-teratogenic effect of folic acid on procarbazine-induced microgenia.     

The relation of aberrant vasculogenesis to skeletal malformation in the hamster fetus

Summary Oral administration of teratogenic doses of retinoic acid to pregnant hamsters on day 10 of gestation is associated with dysmorphogenesis of the appendicular skeleton. During the 24h following retinoic acid treatment, the developing limb bud vasculature was disorganized, with blood vessels encroaching on areas where mesenchymal condensation of the skeletal blastemata normally occurs. Large, branching marginal folds and endothelial cell vesiculations protruded into the blood vessel lumina. It is suggested that the vascular changes observed may affect the concurrent early development of the skeleton and contribute to the skeletal malformation seen in near-term fetuses.