ABSTRACT Development of the mammalian secondary palate involves the growth, elevation, medial elongation and midline fusion of palatal shelves. Recent morphological and molecular studies on palatogenesis suggest that the developing palate is not a homogeneous organ but each part may behave differently during organogenesis. Especially, some key molecules involved in palate development have been shown to exhibit heterogeneous patterns of expression in the palatal tissue. Therefore it seems necessary to recognize the regional heterogeneity of the developing palate along the dorsoventral and anteroposterior axes when analyzing the mechanisms of normal and abnormal morphogenesis. Based on recent studies, we discuss the issue of the regional heterogeneity in the fetal palate and propose a principle that divides the fetal palate into several regions from the morphological and molecular standpoint.
ABSTRACT Spina bifida, anencephaly, and encephalocele are commonly grouped together and termed neural tube defects (NTD). Failure of closure of the neural tube during development results in anencephaly or spina bifida aperta but encephaloceles are possibly post-closure defects. NTD are associated with a number of other central nervous system (CNS) and non-neural malformations. Racial, geographic and seasonal variations seem to affect their incidence. Etiology of NTD is unknown. Most of the non-syndromic NTD are of multifactorial origin. Recent in vitro and in vivo studies have highlighted the molecular mechanisms of neurulation in vertebrates but the morphologic development of human neural tube is poorly understood. A multisite closure theory, extrapolated directly from mouse experiments highlighted the clinical relevance of closure mechanisms to human NTD. Animal models, such as circle tail, curly tail, loop tail, shrm and numerous knockouts provide some insight into the mechanisms of NTD. Also available in the literature are a plethora of chemically induced preclosure and a few post-closure models of NTD, which highlight the fact that CNS malformations are of hetergeneitic nature. No Mendelian pattern of inheritance has been reported. Association with single gene defects, enhanced recurrence risk among siblings, and a higher frequency in twins than in singletons indicate the presence of a strong genetic contribution to the etiology of NTD. Non-availability of families with a significant number of NTD cases makes research into genetic causation of NTD difficult. Case reports and epidemiologic studies have implicated a number of chemicals, widely differing therapeutic drugs, environmental contaminants, pollutants, infectious agents, and solvents. Maternal hyperthermia, use of valproate by epileptic women during pregnancy, deficiency and excess of certain nutrients and chronic maternal diseases (e.g. diabetes mellitus) are reported to cause a manifold increase in the incidence of NTD. A host of suspected teratogens are also available in the literature. The UK and Hungarian studies showed that periconceptional supplementation of women with folate (FA) reduces significantly both the first occurrence and recurrence of NTD in the offspring. This led to mandatory periconceptional FA supplementation in a number of countries. Encouraged by the results of clinical studies, numerous laboratory investigations focused on the genes involved in the FA, vitamin B12 and homocysteine metabolism during neural tube development. As of today no clinical or experimental study has provided unequivocal evidence for a definitive role for any of these genes in the causation of NTD suggesting that a multitude of genes, growth factors and receptors interact in controlling neural tube development by yet unknown mechanisms. Future studies must address issues of gene-gene, gene-nutrient and gene–environment interactions in the pathogenesis of NTD.
ABSTRACT The teratogenic potential of valproic acid has been well established both in experimental models and in human clinical studies. Evidence from many previous studies has shown that VPA is an appropriate drug model for studying chemical structure-teratogenicity relationships. Using molecular techniques of DNA microarray (GeneChip system) or quantitative real-time polymerase chain reaction with low teratogenic VPA analogs as comparative control drugs, we attempted to identify the genes involved with the molecular mechanisms of VPA teratogenicity in the neural tube and the axial skeleton of the mouse embryo. The recent development of DNA microarray enables a genome-wide approach to the identification of genes correlated with the teratogenicity of chemicals (teratogenomics). The VPA-induced changes in gene expression seen during mouse embryogenesis provides information for understanding how VPA disrupts normal embryonic development, and also provides leads for the development of safer medicines.
ABSTRACT The objective of this investigation was to identify the rates for specific birth defects among the offspring of Japanese mothers in Hawaii and compare them to rates among the offspring of white mothers. Cases were all infants and fetuses with any of 54 specific birth defects born to Japanese and white mothers identified by a population-based birth defects registry in Hawaii. The rates were calculated for both racial groups and comparisons made by calculating the rate ratio and 95% confidence interval. The rates among the offspring of Japanese mothers were substantially higher for four of the birth defects (pulmonary valve atresia and stenosis, anomalous pulmonary venous return, cleft lip with/without cleft palate, small intestinal atresia and stenosis) and substantially lower for five of the birth defects (pyloric stenosis, hypospadias and epispadias, renal agenesis and hypoplasia, obstructive genitourinary defect, syndactyly). After adjusting for maternal age, these significantly elevated or lower rates remained. Moreover, the rate was significantly higher among the offspring of Japanese mothers for anotia/microtia, tetralogy of Fallot, and persistent cloaca and significantly lower for transposition of great arteries. The rates for a number of specific birth defects differed between Japanese and white mothers in Hawaii.
ABSTRACT We observed the learning ability in Clock mutant mice with Jcl/ICR background (Clockj), a mice model of evening-type individuals, in the early part of dark phase. In order to estimate the learning ability, Morris water maze (WM) and passive avoidance (PA) test were performed. Release of acetylcholine, 5 hydroxytryptophan (5-HT) and dopamine (DA) in hippocampus was measured by in vivo microdialysis method. Clockj showed the impaired learning ability in the WM, but not in PA test. Hippocampal acetylcholine release was significantly attenuated in the Clockj in comparison to the wild-type mice. Neither 5-HT nor DA in the hippocampus was affected by the Clock mutation. Clock, an essential gene controlling circadian rhythm, may have an important role on the spatial learning and hippocampal cholinergic function, at least, at the beginning of the dark phase.
ABSTRACT Diseases of respiratory system caused by acute infections are among the most common maternal diseases during pregnancy. The objective of the study was to estimate the association between congenital abnormalities and acute respiratory infections during the first trimester of pregnancy. The data set of the Hungarian Case-Control Surveillance of Congenital Abnormalities including 22 843 cases with congenital abnormalities, 38 151 population controls without congenital abnormalities and 834 malformed controls with Down syndrome between 1980 and 1996 was evaluated. 2118 cases with congenital abnormalities (9.3%), 3455 population controls (9.1%) and 92 malformed controls with Down syndrome (11.0%) had mothers with acute respiratory infections. Of 25 different congenital abnormality groups, esophageal atresia/stenosis showed a high adjusted prevalence odds ratios (POR) with 95% confidence interval (CI) for acute respiratory infections during the first trimester of pregnancy in case mothers compared with population controls (3.6, 1.4–9.1) and malformed controls (1.9, 1.0–3.5), respectively. In addition there was an association between medically recorded acute respiratory infections during the first trimester of pregnancy and a higher risk for some other congenital abnormalities, such as posterior cleft palate and multiple congenital abnormalities. In conclusion a possible association between some congenital abnormalities, particularly esophageal atresia/stenosis and maternal acute respiratory infections cannot be excluded due to the interactions of the microbial agents, related drug treatments and last but not least the indirect effect of maternal diseases, such as fever-hyperthermia, hypoxia and dietary deficiency. However, periconceptional multivitamin/folic acid supplementation during the early pregnancy was able to reduce the acute respiratory infection related risk for congenital abnormalities.
ABSTRACT The effects of prenatal exposure to phenobarbital (PB) on the cardiovascular system were examined in rat fetuses and pups. PB was administered at a dose of 80 or 120 mg/kg/day by gavage to Sprague Dawley (SD) rats on two consecutive gestational days (GD): 7–8, 8–9, 9–10, or 10–11. Fetuses were examined for cardiovascular malformations on GD 20. In addition, pups were examined for PB-induced cardiovascular malformations. Incidences of ventricular septal defect (VSD), overriding aorta, double outlet right ventricle and transposition of great arteries were significantly increased in the fetuses whose dams were administered PB at 120 mg/kg on GD 8–9, 9–10 or 10–11. GD 8–11 was the critical period for the cardiovascular malformations associated with administration of PB in rats. Various types of cardiovascular malformations were detected in pups from the PB-administered dam. Severe cardiovascular malformations induced by PB caused deaths on early postnatal days. However, slight malformations such as isolated VSD persisted until weaning, and did not affect postnatal viability.
ABSTRACT DDT, an organochlorine pesticide, has been cited as a representative chemical suspected of having endocrine disrupting effects. In this study, the potential endocrine disrupting activities of p,p′-DDT, a major component of DDT, were investigated in rats in a 2-generation reproduction toxicity study in accordance with the most current test guidelines of the Ministry of Agriculture, Forestry and Fisheries in Japan, Organization for Economic Cooperation and Development (OECD) and United States Environmental Protection Agency (USEPA) with some modifications and additions. p,p′-DDT was given to parental rats at dietary levels of 0, 5, 50 or 350 ppm. Systemic toxicities in the parental animals consisted of tremors and subsequent deaths (females only) and/or pathological alterations of the liver (both sexes of animals) of the 2 higher dose groups. Reproductive and postnatal developmental toxicities were not evident up to the highest dose level except for the decreased pup viability index on postnatal day 21 in the 350 ppm group. Changes in serum estradiol and progesterone levels and/or a delay in male sexual maturation were noted in the 2 higher dose groups in a dose-dependent fashion, suggesting alterations of endogenous endocrine functions. However, these changes never resulted in substantial reproductive disorders.
ABSTRACT When amniocentesis reveals a mosaic karyotype and the baby presents with multiple malformations, an analysis of the baby’s peripheral blood typically reveals a mosaic karyotype. We present a boy who was prenatally diagnosed by amniocentesis as having trisomy 9 mosaicisim but who had normal G-banding results on postnatal blood karyotyping; the patient also exhibited multiple malformations, including a diaphragmatic hernia, arthrogryposis, undescended testes, and characteristic facies. Because of the discrepancy between the phenotype and karyotype, we repeated the chromosomal studies on multiple occasions. Interphase FISH performed on abdominal wall muscle tissue revealed a mosaic trisomy 9 karyotype: 47,XY, + 9(159)/46,XY (19). Based on these findings, we finally diagnosed the patient as having trisomy 9 mosaicism and counseled the parents that the risk of recurrence was low. We conclude that it is important to be aware of the possibility that the patient can have a normal postnatal blood karyotype and an abnormal phenotype with multiple malformations when trisomy 9 mosaicism is detected prenatally. When the baby’s phenotype is abnormal, karyotyping on multiple tissues is useful for confirming clinical impression as well as determining the prognosis and providing accurate genetic counseling.
ABSTRACT This paper reviews the role of the Western Australian Birth Defects Registry in the primary prevention of neural tube defects. The Registry provides complete and up-to-date information on all neural tube defects (NTD), including terminations of pregnancy. These data have been used to determine a baseline rate of NTD and to monitor trends in NTD over time, when health promotion of folic acid supplement use and voluntary fortification of food with folate were introduced. The register has also been used to investigate NTD in special populations (Indigenous infants in Australia) and as a sampling frame for case control studies. The data derived from these studies have been used to assist in assessing whether mandatory food fortification in Australia is indicated to prevent NTD.