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PubMed2002

[Progress in researches on neural tube defects related the genes].

Neural tube defects are common birth defects which are ascribed to the combination of genetic and environmental factors. The genetic factors include cell growth factors,transformation factors and key enzymic genes involved in folate metabolism. This paper reviews the genes as focus of current investigation and the relationship between the genetic polymorphism on the specific sites and neural tube defects based on animal model and population epidemiological study. It indicates that the multifactors play an important role in the etiology of neural tube defects.

English Abstract↗
PubMed1982

Acetylcholinesterase in neural tube defects: a model using chick embryo amniotic fluid.

Acetylcholinesterase was measured in amniotic fluid from normal chick embryos and embryos with neural tube defects. Neural tube defects were induced in the chick embryos by three procedures, removal of albumen, mechanical disruption of the closed neural tube or injection of tetanus toxin. The concentration of acetylcholinesterase in amniotic fluid from untreated normal embryos changed throughout the period examined (5-14 days incubation) but was stable at 0.5 U1(-1) over the time period 6-11 days. Amniotic fluid taken from treated embryos with neural tube defects at 8 days always contained a higher concentration of acetylcholinesterase than fluid from sham operated but otherwise normal embryos, mean 40.9 U1(-1), S.E.M. = 10. U1(-1), versus 1.0 U1(-1), S.E.M. = 0.2 U1(-1). The range of values (6.1-393 U1(-1)) was clearly separated from the normal values, range 0.0-5.5 U1(-1). In 13 cases with developmental abnormalities other than neural tube defects, the concentration of acetylcholinesterase was elevated in only one. Two different forms of acetylcholinesterase, as shown by gel electrophoresis, were present in fluid form both normal and defective embryos. These forms were also present in blood plasma, cerebrospinal fluid and in the high speed supernatant from brain extracts, the latter tissue contained an additional form of greater electrophoretic mobility. After irreversible inhibition, enzyme activity in amniotic fluid recovered slowly; only half the control value was reached by 140 h compared with complete recovery in the tissues of the embryo within 19 h. Histochemical staining for acetylcholinesterase showed that the spinal cord in the region of the lesion contained high concentrations of the enzyme. The possible sources of acetylcholinesterase in amniotic fluid are discussed. This chicken model of neural tube defects provides support for the use of acetylcholinesterase tests in the detection of neural tube defects clinically, and provides a model for experimentation with this system.

Acetylcholinesterase↗
PubMed2005

Loss of mitogen-activated protein kinase kinase kinase 4 (MEKK4) results in enhanced apoptosis and defective neural tube development.

Neural tube defects (NTDs) are prevalent human birth defects. Mitogen-activated protein kinases (MAPKs), such as c-Jun N-terminal kinase (JNK), are implicated in facilitating neural tube closure, yet upstream regulators remain to be identified. Here, we show that MAP kinase kinase kinase 4 (MEKK4) is strongly expressed in the developing neuroepithelium. Mice deficient in MEKK4 develop highly penetrant NTDs that cannot be rescued by supplementation with folic acid or inositol. Unlike most mouse models of NTDs, MEKK4 mutant embryos display genetically co-segregated exencephaly and spina bifida, recapitulating the phenotypes observed in human patients. To identify downstream targets of MEKK4 during neural tube development, we examined the activity of MAP kinase kinase 4 (MKK4), a signaling intermediate between MAP kinase kinase kinase and JNK/p38. We found a significant reduction in MKK4 activity in MEKK4-deficient neuroepithelium at sites of neural tube closure. MAPK pathways are key regulators of cell apoptosis and proliferation. Analyses of the neuroepithelium in MEKK4-deficient embryos showed massively elevated apoptosis before and during neural tube closure, suggesting an antiapoptotic role for MEKK4 during development. In contrast, proliferation of MEKK4-deficient neuroepithelial cells appeared to be largely unaffected. MEKK4 therefore plays a critical role in regulating MKK4 activity and apoptotic cell death during neural tube development. Disruption of this signaling pathway may be clinically relevant to folate-resistant human NTDs.

Animals↗
PubMed1998

The prevention of neural tube defects.

The prevention of neural tube defects is a complex problem. The genetic associations may ultimately allow the prepregnancy identification of women at high risk of a neural tube defect. Education of both the public and healthcare providers has been shown to increase awareness, but the majority of women do not take folic acid before and in the early part of pregnancy. Food fortification will be effective in increasing the folate levels of the population and will have a benefit even at low doses of fortification.

Female↗
PubMedDate not supplied

A cost-benefit analysis of a population screening programme for neural tube defects.

Population screening for neural tube defects is possible by measuring maternal serum alphafetoprotein levels with appropriate follow-up as required. British Columbia has approximately 39 000 births annually and the incidence of neural tube defects is 1.55 per 1000 births (0.94 per 1000 livebirths). Results from a cost-benefit analysis suggest that the outlined screening programme would be cost-beneficial for British Columbia. Other important factors essential to consider before instituting a population screening programme are discussed.

British Columbia↗
PubMed2001

Abnormal folate metabolism and genetic polymorphism of the folate pathway in a child with Down syndrome and neural tube defect.

The association of neural tube defects (NTDs) with Down syndrome (trisomy 21) and altered folate metabolism in both mother and affected offspring provide a unique opportunity for insight into the etiologic role of folate deficiency in these congenital anomalies. We describe here the case of a male child with trisomy 21, cervical meningomyelocele, agenesis of corpus callosum, hydrocephaly, cerebellar herniation into the foramen magnum, and shallow posterior cranial fossa. Molecular analysis of the methylenetetrahydrofolate (MTHFR) gene revealed homozygosity for the mutant 677C-->T polymorphism in both the mother and child. The plasma homocysteine of the mother was highly elevated at 25.0 micromol/L and was associated with a low methionine level of 22.1 micromol/L. Her S-adenosylhomocysteine (SAH) level was three times that of reference normal women, resulting in a markedly reduced ratio of S-adenosylmethionine (SAM) to SAH and significant DNA hypomethylation in lymphocytes. The child had low plasma levels of both homocysteine and methionine and a reduced SAM/SAH ratio that was also associated with lymphocyte DNA hypomethylation. In addition, the child had a five-fold increase in cystathionine level relative to normal children, consistent with over-expression of the cystathionine beta synthase gene present on chromosome 21. We suggest that altered folate status plus homozygous mutation in the MTHFR gene in the mother could promote chromosomal instability and meiotic non-disjunction resulting in trisomy 21. Altered folate status and homozygous TT mutation in the MTHFR gene in both mother and child would be expected to increase the risk of neural tube defects. The presence of both trisomy 21 and postclosure NTD in the same child supports the need for an extended periconceptional period of maternal folate supplementation to achieve greater preventive effects for both NTD and trisomy 21.

Amino Acids, Sulfur↗
PubMedDate not supplied

[Folic acid in the prevention of neural tube defects].

INTRODUCTION: The term neural tube defects (NTD) stands for anencephaly, iniencephaly, cephalocoele and spina-bifida. The cause of these anomalies is failure of brain spinal cord to properly develop, together with their protective shield of skull and spine, around the 4th gestational week. The prevalence of NTD in continental Europe is 11.2 10,000 live births. THE LEVEL OF FOLATES IN SERUM AND NTD: The level of folates in serum can influence the risk of a child affected with NTD. Studies on women with previous pregnancies with NTD showed that supplementary intake of folic acid, with or without other vitamins, preconceptual period throughout the first trimester has a preventive effect on its recurrence. Inadequate intake of folic acid is also connected with preterm delivery, intrauterine growth retardation and placental abruption and infarction. FOLATES IN NUTRITION: It is not folic acid, but folates, from the vitamin B group, that can naturally be found in food. There are several groups of folates that differ in the quantity by which they can be absorbed from food. Folates are temperature and storage sensitive and cooking can cause a significant fall of their concentration in food. FOLIC ACID SUPPLEMENTATION: The mean daily intake of folates by food is 0.218 mg whereas a reference nutritive intake for a woman of reproductive age is 0.2 mg per day. The currently recommended daily dose for prevention of first NTD occurrence is 0.4 mg, so it is clear that a certain amount of folic acid has to be supplemented preconceptionally and during the first trimester. It can be done in two ways, by telling all women to take it before conceiving, or to fortify food with sufficiently high doses of folic acid in order to achieve adequate serum levels. Neither of the ways is ideal, for not all women would take the supplement, and by aggressively fortifying the food, we create a potential hazard to those that do not need it and may have some problems with the excess of it. The best solution would be a widespread campaign about the need for folic acid and the risks of NTD. CONCLUSION: Recommendations of The Expert Advisory Group on Folic Acid in prevention of neural tube defects has several aspects (1) reducing the risk of the first NTD occurrence by preconceptional vitamin supplementation of folic acid in the dose of 0.4 mg day, which would go on until the end of the 12th week (2) reducing the risk of NTD recurrence in offspring of men and women with spina-bifida or with obstetric history affected with NTD by preconceptional vitamin supplementation of folic acid in the dose of 4 mg daily during the first 12 weeks and (3) organizing educational programmes for medical staff as well as the whole population in order to popularize vitamin supplementation.

Female↗
PubMed1998

[Prevention using folic acid--a good method for reduction of neural tube defects in Poland].

Incidence of neural tube defects in Poland in the 90's was 2.68 in 1000 births. The value of incidence has not been changed within last twenty years. Mortality caused by neural tube defects in Poland is much higher than in many other European countries and the United States. High rates of incidence of neural tube defects in Poland is probably caused by low utilisation of methods of secondary prevention in a group of low-risk pregnant women. Since methods of primary prevention of neural-tube defects are available; primary prevention with folic acid, should be immediately implemented in Poland.

Adult↗
PubMed1992

Neural tube defects--prenatal diagnosis and management.

Neural tube defects rank second to congenital heart disease as a major cause of congenital malformation. Recent developments in ultrasound have improved prenatal diagnosis. Due to anomaly scans at 18 weeks gestation and the availability of a genetic clinic, prenatal diagnosis of neural tube defects at the Royal Maternity Hospital was 91.2% during 1987-1989. However, only 50% of parents accept termination of pregnancy and it is questionable if prenatal diagnosis is of benefit to those who wish to continue with the pregnancy. Parents may accept the situation better at birth, having had time to come to terms with it, helped with support from the obstetrician, clinical geneticist, paediatrician, genetic nurse and social worker. For some affected fetuses who have better muscle function and leg movement at term it appears from the literature that the outcome may be improved by caesarean section delivery. In Ireland fetuses with neural tube defects will continue to be delivered, as termination is unacceptable to many, but despite this there may be a positive benefit from prenatal diagnosis of neural tube defects. Prospective randomised controlled trials are needed to confirm benefit from delivery by caesarean section for fetuses with a good prognosis. As a result of prenatal diagnosis of a neural tube lesion the fetus should enjoy benefit in terms of physical morbidity, and the parents should benefit in terms of psychological morbidity.

Abortion, Induced↗
PubMed1987

Prenatal diagnosis policy without routine amniocentesis in pregnancies with a positive family history for neural tube defects.

The recurrence risk for neural tube defects in pregnancies of women with a family history of neural tube defects greatly exceeds the general population risk. In these high risk pregnancies, we used a prenatal diagnostic method differing from that usually employed, relying mainly on the results of maternal serum alpha-fetoprotein (MSAFP) and ultrasound examination, without routine amniocentesis. During the 6 years reviewed in this study, this method was applied in 539 pregnancies. Of a total of 20 neural tube defects, 19 were detected using this combination of MSAFP, ultrasound, and selective amniocentesis, and the authors estimate that about 8-10 spontaneous abortions were avoided because only 28 amniocenteses were carried out instead of 539. The risk of recurrence was found to be lower than that experienced earlier.

Amniocentesis↗
PubMed1985

Maternal serum alpha-fetoprotein screening for neural tube defects. Report of a combined study in Germany and short overview on screening in populations with low birth prevalence of neural tube defects.

The basis of maternal serum alpha-fetoprotein (AFP)-screening for neural tube defects is discussed. A report is given of a large scale screening study in the Federal Republic of Germany combining the experiences in Giessen and Hannover on over 50,000 pregnant women, about evenly distributed among both centers. Published and known forthcoming data from other low incidence populations, particularly of European countries, are reviewed briefly. The conclusion is reached that general screening could effectively be instituted and in the final result should also be cost-beneficial.

Amniotic Fluid↗
PubMed1998

Prevention of neural tube defects: vitamins, enzymes and genes.

Neural tube defects can be prevented by folic acid, although the mechanism of this action is unclear. Studies of a series of folate-related enzymes have so far failed to pin-point the nature of the metabolic defect in the neurulation-stage embryo that is corrected by folic acid. Approximately 30% of neural tube defects appear resistant to folic acid and recent work in a mouse genetic model system suggests that administration of myo-inositol may be a complementary therapeutic option. The large number of mouse genes known to cause neural tube defects provide a starting point for identifying the genetic basis of the human defects.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1999

Folic acid supplementation of pregnant mice suppresses heat-induced neural tube defects in the offspring.

Neural tube defects (NTD) are a group of malformations that result from the failure of the neural tube to close early in embryonic development and among the most common congenital malformations in humans. It has been reported that a substantial proportion of NTD in humans can be prevented by folic acid (FA) supplementation prior to conception and during the first months of pregnancy, and myo-inositol (MI) was shown to reduce the incidence of NTD in curly tail mice which are not prevented by FA. Brief maternal hyperthermia (HT) early in pregnancy has been implicated in NTD both in humans and laboratory animals, and anterior NTD including exencephaly and anencephaly are induced frequently when pregnant mice are exposed to HT. We examined the effect of FA or MI supplementation of pregnant mice on the occurrence of heat-induced NTD in the offspring. When pregnant mice were treated with FA (3 mg/kg) daily from gestational day (GD) 0.5 through GD 9.5 and heated at GD 8.5, the prevalence of NTD in the fetuses (26.6%) was significantly lower than the corresponding figure in the HT alone group (38.6%; P < 0.05). However we failed to detect the preventive effect of MI (500 mg/kg). The results of this study suggest that prenatal FA supplementation decreases HT-induced NTD in mice and sufficient FA intake during early pregnancy may be recommended to avoid the birth of malformed children.

Analysis of Variance↗
PubMed2003

[Prevention of neural tube defects with folic acid].

Neural Tube Defects (NTD's) include a large number of congenital malformations produced when the open neural tube presents a very early stages in the development of the human embryo fails to close on or before the first month post conception. NTD's are considered to be one of the most common forms of malformations with varying degrees depending of genetic and environmental conditions. The studies prove that the additional taken of folic acid plays an important role against the NTD's. Numerous studies prove this "B" vitamin has an important protective effect not only for the recurrence of NTD's, but for new cases too. In light of these, in 1992 the US Public Health Services issued the recommendation that all women in child-bearing age should consume at least 0.4 mg (400 micrograms) of folic acid daily.

Female↗
PubMed1991

The changing incidence of neural tube defects in Scotland.

The impact of neural tube defects on neonatal surgery has been declining in Scotland over the past two decades. The Scottish statistics for neural tube defects were studied from 1971 to 1988. The incidence of neural tube defects in Scotland has declined from 5.50 to 1.10 per 1,000 births over this period (3.00 to 0.58 per 1,000 births for spina bifida and 2.50 to 0.52 per 1,000 births for anencephaly). Antenatal maternal alpha-fetoprotein (AFP) screening was introduced to Scotland on a wide scale in 1976. The number of terminations for anencephaly peaked in 1980 (85), and for spina bifida in 1981 (70), and both have since declined. The Scottish birth rate has been about 67,000 per year over this period. The declining incidence of neural tube defects is not explained by the effect of antenatal screening and terminations alone. A downward trend was apparent before 1976, and although antenatal screening has had a considerable impact on anencephaly births (peak terminations 89% in 1983), it has had only a modest impact on spina bifida births (peak terminations 53% in 1984). We conclude that the natural decline in incidence of neural tube defects is the major factor in the observed decline in neonatal surgical admissions for these defects.

Abortion, Eugenic↗
PubMedDate not supplied

Neural tube defects: epidemiology, detection, and prevention.

Neural tube defects are common congenital malformations of the central nervous system and include anencephaly, spina bifida, and encephalocele. Prenatal detection by amniotic fluid analysis of alpha-fetoprotein is possible in those women known to be at high risk for neural tube defects. Maternal serum screening for increased alpha-fetoprotein levels is now available nationally and has the potential to identify women who otherwise would not be known to be at risk. The epidemiology, detection, screening, and prevention of neural tube defects are discussed, and an explanation of alpha-fetoprotein and its use in screening is offered.

Acetylcholinesterase↗
PubMed1982

Etiologic heterogeneity of neural tube defects: clues from epidemiology.

The epidemiology of neural tube defects was reviewed, using data from two birth defects surveillance systems: the nationwide Birth Defects Monitoring Program and the Metropolitan Atlanta Congenital Defects Program, for 1970-1978 and 1968-1979, respectively. After excluding cases with recognized causes, neural tube defects were divided into two major groups: "singles" and "multiples," depending on the presence of associated major defects. Only singles, which accounted for the majority of cases, were shown to have the well-known epidemiologic characteristics of neural tube defects: marked predominance of females and whites, geographic variation with an east-to-west gradient, and decreasing rates over time. On the other hand, multiples had no excess of females and occurred less predominantly in whites; moreover, their rates showed no geographic variation and little or no downward trends over time. The presence of associated defects indicates that neural tube defects are epidemiologically and probably etiologically heterogeneous. It is suggested that analytic studies of neural tube defects may be more rewarding if they try to identify different risk factors associated with various subgroups. This approach to the study of birth defects may provide better clues to their etiology and pathogenesis.

Chromosome Aberrations↗
PubMed2003

Pharmacology of neural tube defects.

The pharmacology of neural tube defects (NTDs) is a complex issue. Several theories regarding the etiology of NTDs emphasize the importance of interactions between genetic, environmental, and biochemical factors at a key point in time. One such factor is chronic drug therapy, a potential consequence of which is the formation of toxic drug metabolites, including free radicals (FRs), which have been implicated in the etiology of NTDs. Under normal physiological conditions, FRs are quickly destroyed by antioxidant defense systems. However, FR-mediated cellular damage can occur if these defense systems fail or are overburdened, such as in patients who are genetically deficient in FR scavenging enzyme activity (FRSEA) or who are receiving chronic drug therapy. Congenital defects, including NTDs, resulting from FR-induced damage have been reported in both experimental animals and humans. For example, the use of antiepileptic drugs (AEDs) during pregnancy that have the propensity to form FRs during their metabolism are associated with an increased risk of the development of congenital malformations, including NTDs. This article reviews the biochemistry of FRs, the factors regulating FR scavenging capacity, and the theories regarding the etiology of NTDs; presents a hypothesis of a unified mechanism for AED-induced NTDs and other congenital defects; and briefly discusses the roles of folate and selenium in the prevention of NTDs.

Anticonvulsants↗