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PubMed1988

A cell-type-specific abnormality of cell proliferation in mutant (curly tail) mouse embryos developing spinal neural tube defects.

The mouse mutant curly tail (ct) provides a model system for studies of neurulation mechanisms. 60% of ct/ct embryos develop spinal neural tube defects (NTD) as a result of delayed neurulation at the posterior neuropore whereas the remaining 40% of embryos develop normally. In order to investigate the role of cell proliferation during mouse neurulation, cell cycle parameters were studied in curly tail embryos developing spinal NTD and in their normally developing litter-mates. Measurements were made of mitotic index, median length of S-phase and percent reduction of labelling index during a [3H]thymidine pulse-chase experiment. These independent measures of cell proliferation rate indicate a reduced rate of proliferation of gut endoderm and notochord cells in the neuropore region of embryos developing spinal NTD compared with normally developing controls. The incidence of cell death and the relative frequency of mitotic spindle orientations does not differ consistently between normal and abnormal embryos. These results suggest a mechanism of spinal NTD pathogenesis in curly tail embryos based on failure of normal cell proliferation in gut endoderm and notochord.

Animals↗

PubMed1987

Parental attitudes to the unclosed open neural tube defect.

Recent years have seen a trend away from the immediate closure to delayed or nonclosure of the back lesion in open neural tube defects (ONTD). Parental attitudes towards this more conservative surgical policy have not been investigated. We therefore surveyed 70 families in Northern Ireland of children who are still alive, over six months of age who had an ONTD which was not surgically closed immediately after birth. Fifty-eight parents (84%) responded. Most parents (84%) had no difficulty in handling or dressing the back, but three-quarters felt that the lesion was painful and 41% felt that its appearance was disturbing to other members of the family. In those who had delayed closure (n = 15) all parents confirmed that the child was more comfortable and easier to handle afterwards. Eleven of them (73%) felt that the child was more acceptable to the rest of the family and that surgery should have been carried out earlier. A third preferred immediate closure "to make the child more comfortable" and to "improve the general quality of life". However, 46% did not want surgery for fear of upsetting the status quo. This survey suggested that parental attitudes towards the open back lesion differ greatly and that these views should play a greater role in the decisions which influence the timing of closure of ONTD.

Attitude↗

PubMed1992

Inositol deficiency increases the susceptibility to neural tube defects of genetically predisposed (curly tail) mouse embryos in vitro.

Curly tail (ct/ct) mouse embryos, which have a genetic predisposition for neural tube defects (NTD), were grown in culture from the 2-5 somite stage, before the initiation of neurulation, up to the 22-24 somite stage, when closure of the anterior neural tube is normally complete. The embryos were cultured in whole rat serum or in extensively dialysed serum supplemented with glucose, amino acids, and vitamins, with inositol omitted or added at concentrations of 2, 10, 20, and 50 mg/l. Two strains were used as controls; CBA mice, which are related to curly tails, and an unrelated PO stock. It was found that ct/ct embryos were particularly sensitive to inositol deficiency; both they and the CBA embryos showed a similar high incidence of cranial NTD after culture in inositol deficient medium (12/17 and 11/18, respectively). Furthermore, the lowest dose of inositol had no effect on the frequency of head defects in ct/ct mice, though it halved the incidence in CBA embryos. With higher inositol concentrations, the majority of ct/ct embryos completed head closure normally, and their development was generally similar to that obtained in whole serum. PO embryos showed a lower proportion (5/19) of cranial NTD in the inositol deficient medium than the other two strains, and this was further reduced by even the lowest inositol dose.

Animals↗

PubMed2000

Association between historically high frequencies of neural tube defects and the human T homologue of mouse T (Brachyury).

The human T developmental gene has been implicated in the etiology of neural tube defects (NTDs) on the basis both of mouse studies of its homologue, T (Brachyury), and of allelic association in a Caucasian population. We have investigated the frequency of the T allelic variant TIVS7-2 in 218 Irish NTD case-parent triads. This population showed the same trend as previously reported, with an excess of the TIVS7-2 allele among cases. Log-linear modeling of case and maternal genotypic effects within families indicated that TIVS7-2 was elevated in cases (relative risk, RR = 1.36) but not in mothers (RR = 0.91). The TIVS7-2 allele is markedly associated with cases born before 1980 (RR = 2.09; CI = 1.23-3.55; corrected p = 0.030), but not with more recent cases (RR = 0.92). Cases carrying a TIVS7-2 allele did not show any increased tendency to be homozygous for the thermolabile variant of the folate-dependent enzyme 5,10-methylene tetrahydrofolate reductase, which is an established genetic risk factor for NTDs. Since the incidence of NTDs has declined markedly in Ireland over the last few decades, we suggest that the T-associated risk is potentiated by nutritional or environmental risk factor(s), the impact of which have been diminishing over time.

Adolescent↗

PubMed1983

The effect of periconceptional supplementation on blood vitamin concentrations in women at recurrence risk for neural tube defect.

1. We measured erythrocyte folic acid and riboflavin, serum folic acid and leucocyte vitamin C in women at high risk for neural tube defect (NTD) recurrence who were receiving periconceptional vitamin supplementation, before they received extra vitamins, after 28 d of supplementation and at the 8th week of pregnancy. Blood vitamin concentrations in unsupplemented high-risk women were also compared with the values found in unsupplemented low-risk women. 2. Vitamin supplementation with Pregnavite Forte F (Bencard) raised the mean values for all vitamins measured by the 8th week of pregnancy. Mean erythrocyte folic acid rose from 250 to 478 ng/ml; plasma folic acid from 8.4 to 26.1 ng/ml; leucocyte vitamin C from 1.82 to 3.21 micrograms/ml blood; erythrocyte riboflavin (glutathione reductase (EC 1.6.4.2) activation ratio) from 1.08 to 1.04. All women receiving supplements had increased their serum and erythrocyte folic acid levels above the highest values found in women in an earlier study, who subsequently gave birth to children with NTD. Not all women, however, increased their leucocyte ascorbic acid or erythrocyte riboflavin levels above the highest values. 3. When vitamin concentrations in unsupplemented high-risk women compared with levels in unsupplemented women at low risk for NTD, no significant differences were found in the mean values. However, a significantly higher proportion of high-risk compared with low-risk women had erythrocyte folic acid and leucocyte vitamin C values on or below the 5th percentile of the adult normal range. 4. The effectiveness of Pregnavite Forte E (Bencard) for increasing maternal vitamin reserves is discussed with a view to preventing NTD and the possibility of identifying groups at risk for NTD because of low blood vitamin levels is considered.

Ascorbic Acid↗

PubMed2005

[Prevention of neural tube defects with periconceptional folic acid supplementation in Europe].

The conclusion of a report recently published by EUROCAT is that the potential for preventing neural tube defects with periconceptional folic acid supplementation is still far from being fulfilled in Europe. A number of recommendations to increase periconceptional folate status are made. In Denmark less than 20% of pregnant women follow the official recommendations on periconceptional folic acid supplementation, making the conclusions of the EUROCAT report relevant.

Denmark↗

PubMed1999

Maternal occupational and hobby chemical exposures as risk factors for neural tube defects.

In a case-control study, we investigated whether occupational and nonoccupational (hobbies) chemical exposures to women in the periconceptional period increased their risk for having neural tube defect-affected pregnancies. Women were asked about occupational tasks and hobbies performed during the 3 months before through 3 months after conception. Based on her reported occupational tasks and hobbies, an industrial hygienist assigned a priori defined exposure categories to each task and hobby. The exposure categories included 74 chemical groups, 9 "end-use" chemical groups, and organic solvents. Face-to-face interviews were conducted with mothers of 538 (88% of eligible) infants or fetuses with neural tube defect and mothers of 539 (88%) randomly selected, nonmalformed, live-born infants from a population-based 1989-1991 cohort of California births (N = 703,518). Our results suggested that maternal exposures in the periconceptional period to a variety of chemicals associated with occupational and nonoccupational activities did not contribute substantially to risk of neural tube defects in offspring. We observed no effect estimate greater than 2.0 for maternal exposures to the chemical agent groups studied. We did not observe substantially elevated risks associated with maternal exposures to any of the end-use chemical groups or to organic solvents. Considering occupational exposures only among women who worked did not substantially alter results. Adjustment for maternal vitamin use, race/ethnicity, or education level also did not substantially alter the observed associations.

California↗

PubMed1981

Congenital hydrocephalus in two pregnancies following the birth of a child with a neural tube defect: aetiology and management.

A family is described with congenital hydrocephalus occurring in two pregnancies following the birth of a child with a neural tube defect (NTD). Prenatal diagnosis of hydrocephalus at mid-gestation was achieved by ultrasonography. The increased frequency of hydrocephalus among sibs of probands with a NTD and vice versa suggests that, following the birth of a child with either malformations, subsequent pregnancies should be monitored at mid-gestation by amniotic fluid AFP and serial ultrasound examination.

Female↗

PubMed2002

Temporal and spatial patterns of glial differentiation in the surgically induced spinal open neural tube defect of chick embryos: astrocytic, radial glial and microglial differentiations.

INTRODUCTION: There are controversies over the pattern of glial differentiation in spinal open neural tube defect (ONTD) at the prenatal stage. A surgical model of ONTD allows a more precise comparison of glial differentiation between the ONTD and control groups than chemical and genetic models. MATERIALS AND METHODS: To investigate the influence of ONTDs on the patterns of glial differentiation, ONTDs were induced by surgery using Hamburger and Hamilton stage 18 or 19 chick embryos. The spinal cord tissues on postoperative days (POD) 5, 7, 10, and 14 were processed to observe astrocytic, radial glial, and microglial differentiations by glial fibrillary acid protein (GFAP), vimentin and ricinus communis agglutinin-I (RCA-I) stainings, respectively. Four embryos were assigned to subgroups of each POD. Control embryos ( n=4) were staged but the neural tubes were not incised. RESULTS: In the control group, GFAP positivity was shown faintly at the dorsal midline on embryonic day (E) 10 (corresponding to POD 7), in the ventral one-third of the white matter on E 13 and in the whole white matter on E 17. Embryos with ONTDs showed earlier and stronger GFAP positivity from POD 7-14, especially at the dorsal surface and the adjacent gray matter. In the control group, vimentin staining demonstrated a positive reaction at the midline with positivity in a faint, radial pattern on E 8 and E 10. This had all disappeared by E 13 and 17. In embryos with ONTDs, vimentin positivity was enhanced and persisted from POD 5-14. These findings were prominent along the dorsal surface of ONTDs. No difference in RCA-I staining was found between the control and ONTD groups. CONCLUSION: The results reveal that ONTD promotes astrocytic differentiation and prolongs expression of radial glial fibers, which seems to be a reaction to the damage caused by exposure of the spinal cord tissue to amniotic fluid.

Animals↗

PubMed1999

Neural tube defects along the Texas-Mexico border, 1993-1995.

In response to a 1991 anencephaly cluster in Cameron County, Texas, a surveillance and neural tube defect (NTD) recurrence prevention project for NTDs was implemented in the 14 Texas-Mexico border counties. For 1993-1995, NTD-affected pregnancies were identified at all gestational ages through active surveillance of multiple case-ascertainment sources. There were 87 cases of anencephaly, 96 cases of spina bifida, and 14 cases of encephalocele for respective rates of 6.4, 7.1, and 1.1 per 10,000 live births. Of the 197 NTD case-women, 93% were Hispanic. The overall, Hispanic, and Anglo NTD rates were, respectively, 14.6, 14.9, and 10.6 per 10,000 live births. The NTD rate for El Paso County (9.8 per 10,000), the most northwestern Texas county, was significantly lower (p = 0.001) than the aggregate rate for the rest of the Texas border (17.1 per 10,000). The overall Texas border rate was significantly higher (p < 0.001) than a recently estimated rate of 9.3 for California and minimally higher than a recently adjusted rate of 11.3 for the Metropolitan Atlanta Congenital Defects Program counties (p = 0.052), both of which now reflect all gestational ages. Of the 197 Texas border cases, 85% (168 cases) reached a gestational age of > or =20 weeks. Excluding cases of <20 weeks' gestation in the rate had a more marked effect on reducing the anencephaly rate (4.9 per 10,000) than the spina bifida rate (6.7 per 10,000). A country of birth was known for 153 (83%) of the 184 Hispanic case-women: 63% were born in Mexico; 24%, in Texas; and 11%, elsewhere in the United States. Rates for Mexico-born Hispanic women (15.1 per 10,000) were significantly higher than rates for United States-born Hispanic women (9.5 per 10,000) (p = 0.006).

Adult↗

PubMed2000

The study of neural tube defects after the Human Genome Project and folic acid fortification of foods.

The implementation of folic acid fortification will eliminate a proportion of neural tube defects (NTD). As a result, the etiologic and clinical profiles of the developmental disorder may both change. In the assessment of NTD as it evolves, the bioinformatics structure and content of the Human Genome Project will find vital application. One important development will be an enhanced understanding of the role of folic acid in global regulation of gene expression through epigenetic processes. In addition, bioinformatics will facilitate coordination of research in the basic sciences with clinical investigations to better define remaining etiologic factors.

Animals↗

PubMed1992

Folate supplements prevent recurrence of neural tube defects.

In a multicenter, randomized, double-blind intervention study, 4 mg of folate daily given around the time of conception significantly reduced the recurrence of neural tube defects. Supplementation with a folate-free multiple vitamin did not reduce the recurrence rate.

Female↗

PubMed1983

Incidence of neural tube defects in liveborn and stillborn infants in British Columbia over a 10-year period.

Reports of an apparent decline in the incidence of neural tube defects (NTDs) have come from various parts of the world. If these findings are consistent they would have an important impact on prenatal diagnosis and on screening programs. The incidence of NTDs over a 10-year period was examined in British Columbia, a province that has a population-based health surveillance registry through which there is virtually complete ascertainment of liveborn infants with NTDs. The results showed a significant decrease in incidence only for stillborn infants with anencephaly. The increased use of ultrasonography and the subsequent termination of pregnancies in which the fetus has been found to have anencephaly may explain this observation.

Anencephaly↗

PubMed1991

Neural tube defects, maternal cohorts, and age: a pointer to aetiology.

The effects of maternal year of birth and age on the declining prevalence of neural tube defects after 1972-3 were examined using 403 cases ascertained in a prospective study in the Fylde of Lancashire during 1957-89. Matched case-control data were analysed using conditional logistic regression analysis. The risk of an anencephalic baby was significantly greater for older mothers, but changes in the maternal age distribution in the population did not appear to be relevant to the recent decline in prevalence. Antenatal diagnosis and termination of pregnancy was the major cause. Mothers born before 1950 were at significantly greater risk of producing a baby with spina bifida or cranium bifidum. We suggest that abandonment of mercury as a therapeutic agent for infants in the early 1950s is a possible factor in the current decline of these malformations.

Adult↗

PubMed1994

Female predisposition to cranial neural tube defects is not because of a difference between the sexes in the rate of embryonic growth or development during neurulation.

The susceptibility of females to anencephaly is well established and has been suggested to result from a slower rate of growth and development of female embryos during cranial neurulation. We have tested this hypothesis by measuring the rates of growth and development, both in utero and in vitro, of male and female embryos of the curly tail (ct) mutant mouse strain, in which cranial neural tube defects occur primarily in females. Embryonic growth was assessed by increase in protein content, while development progression was judged from increase in somite number and morphological score. Embryos were sexed by use of the polymerase chain reaction to amplify a DNA sequence specific to the Y chromosome, and by sex chromatin analysis. We find that, during neurulation (between 8.5 and 10.5 days of gestation), males are advanced in growth and development relative to their female litter mates, but that the rates of growth and development do not differ between the sexes during this period. We conclude that rate of embryonic growth and development is unlikely to determine susceptibility to cranial neural tube defects. It seems more likely that male and female embryos differ in some specific aspect(s) of the neurulation process that increases the susceptibility of females to development of anencephaly.

Animals↗

PubMed1979

HLA-A,B compatibility in parents of offspring with neural-tube defects or couples experiencing involuntary fetal wastage.

To test the contribution of a putative human analogue of the murine T locus to neural-tube defects (N.T.D.) and involuntary fetal wastage, HLA-A, B compatibility between husband and wife was studied in a group of 77 couples with known obstetric histories. The frequency of sharing of HLA-A,B antigens was significantly higher in 13 couples with recurrent fetal loss at one gestational age and in 11 couples whose offspring had had a lethal N.T.D. than in 17 couples with three or more normal pregnancies. The extent of HLA compatibility--that is, the number of antigens shared by husbands and wives--was significantly higher in 16 couples with one spontaneous abortion, 23 couples with recurrent spontaneous abortions, and 21 couples with N.T.D. offspring than in controls. These data are consistent with a contribution of a locus in or near the HLA complex to N.T.D. and involuntary fetal wastage.

Abortion, Spontaneous↗

PubMed1995

Folate levels and neural tube defects. Implications for prevention.

Using data from a recent case-control study, a woman's risk of having a child with a neural tube defect (NTD) was found to be associated with early pregnancy red cell folate levels in a continuous dose-response relationship. These findings were used to calculate the reduction in NTD cases that would be expected under two different strategies to raise folate levels. Targeting high-risk individuals has a small effect on the population prevalence but can substantially change an individual's risk. Targeting the population produces a small change in individual risk but has a large effect on the population prevalence. Supplementation of high-risk women would be the most efficient method to implement the high-risk strategy, while food fortification would be preferable for the population approach. The current guidelines for the prevention of NTD are for an increased folic acid intake of 0.4 mg per day. This would result in a 48% reduction in NTDs, which may be near optimal. The two intervention strategies should be considered complementary in prevention of NTDs.

Case-Control Studies↗

PubMed2000

[Prevalence of neural tube defects in births before and after promotion of periconceptional folic acid supplementation].

OBJECTIVE: To describe the incidence and the expected clinical picture of neural tube defects (NTD) in years when periconceptional folic acid use increased. DESIGN: Descriptive. METHOD: Data on the prevalence of NTD in the Netherlands in 1994-1998 and on the prognosis at the time of the report obtained from the Nederlands Signalerings Centrum Kindergeneeskunde (Netherlands Paediatric Spotting Centre), where all practising physicians in the Netherlands monthly report children in whom a rare disease has been diagnosed. Prevalence figures from before and after 1996 were compared, because periconceptional use of folic acid increased since late 1996. RESULTS: In 1994-1998, 414 children with NTD were reported, 164 boys, 191 girls and 59 unreported. The prevalence of NTD was 4.6 per 10,000 live births (95% confidence interval (CI): 3.7-5.6) compared with 3.8 per 10,000 live births (95% CI: 2.9-4.6) in the period 1997-1998. Of the 414 children, 257 had a meningomyelocele; the early mortality in this group amounted to 37%. Hydrocephalus was found in 84.8% of the infants, 40.9% of the infants were believed never be able to sit, stand, and walk. CONCLUSION: The prevalence of NTD was lower in the period 1997-1998 than in the period 1994-1996 although the difference was not statistically significant.

Female↗