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PubMed1976

Prenatal diagnosis of neural tube defects. I. Problems and pitfalls: analysis of 2495 cases using the alpha-fetoprotein assay.

The alpha-fetoprotein (AFP) assay is now an established tool for the prenatal diagnosis of neural tube defects (NTDs). About 90% of these defects are diagnosable prenatally early in the second trimester, the other 10% consisting of closed lesions that are not amenable to this approach. From the analysis of our 2495 consecutive cases, 49 NTDs were diagnosed with AFP levels 3 SD above the mean. One closed NTD sample, as expected, did not have an elevated AFP level. Various other fetal disorders or conditions were also associated with elevated AFP levels. AFP assays on amniotic fluids from 1858 patients without a family history of NTD and studied primarily for fetal karyotyping yielded a frequency of 1 NTD in 310 cases. Any amniotic fluid study in the second trimester of pregnancy should include an assay for AFP.

Abnormalities, Multiple↗
PubMed2000

Food labeling: health claims and labeling statements; dietary fiber and cancer; antioxidant vitamins and cancer; omega-3 fatty acids and coronary heart disease; folate and neural tube defects; revocation. Food and Drug Administration, HHS. Final rule.

The Food and Drug Administration (FDA) is revoking its regulations codifying the agency's decision not to authorize the use of health claims for four substance-disease relationships in the labeling of foods, including dietary supplements: Dietary fiber and cancer, antioxidant vitamins and cancer, omega-3 fatty acids and coronary heart disease, and the claim that 0.8 milligram (mg) of folate in dietary supplement form is more effective in reducing the risk of neural tube defects than a lower amount in conventional food. This action is being taken in response to a decision of the U.S. Court of Appeals for the D.C. Circuit invalidating these regulations and directing FDA to reconsider whether to authorize the four health claims. This action will result in the removal of the regulations but does not constitute FDA authorization of the four claims. FDA is completing its reconsideration of the claims and expects to issue decisions on all four claims by October 10, 2000.

Antioxidants↗
PubMed2006

Anticonvulsant activity, neural tube defect induction, mutagenicity and pharmacokinetics of a new potent antiepileptic drug, N-methoxy-2,2,3,3-tetramethylcyclopropane carboxamide.

N-methoxy-2,2,3,3-tetramethylcyclopropane carboxamide (OM-TMCD) is a methoxyamide derivative of a cyclopropyl analogue of valproic acid (VPA). The structural considerations used in the design of OM-TMCD were aimed to enhance OM-TMCD anticonvulsant potency (compared to VPA) and to prevent VPA's two life-threatening side effects, i.e., induction of neural tube defects (NTDs) and hepatotoxicity. Following i.p. administration to rats OM-TMCD demonstrated a broad spectrum of anticonvulsant activity and showed better potency than VPA in the maximal electroshock seizure and subcutaneous pentylenetetrazole tests as well as in the hippocampal kindling model. OM-TMCD was inactive in the mouse 6-Hz test at 100 mg/kg dose. Teratogenicity studies performed in a SWV/Fnn-mouse model for VPA-induced-exencephaly showed that on the equimolar basis OM-TMCD possesses the same fetal toxicity and ability to induce NTDs as VPA, but since OM-TMCD is a much more potent anticonvulsant its activity/exencephaly formation ratio appears to be much more beneficial than that of VPA. OM-TMCD was found to be non-mutagenic and non-pro-mutagenic in the Ames test. It showed a beneficial pharmacokinetic profile in rats, having a high oral bioavailability of 75% and satisfactory values of clearance and volume of distribution. These results support further studies to fully characterize the therapeutic potential of OM-TMCD.

Abnormalities, Drug-Induced↗
PubMed1997

Fractionated-dose effect of X-irradiation on the induction of neural tube defects in mice.

This experiment examined whether mouse embryos have a radio-adaptive response to the induction of malformations. Pregnant Slc:ICR mice were exposed to 0.05 Gy X-radiation followed by 0.5 or 1.0 Gy 4 hr later on day 8 of pregnancy. To compare this with the effect of single doses, four other groups were exposed to 0.5, 0.55, 1.0 or 1.05 Gy. All dams were put to death on day 18, and fetuses were examined for malformations. The frequency of neural tube defects induced by the fractionated irradiation into 0.05 Gy and 1.0 Gy was significantly higher than that induced by single doses of 1.0 and 1.05 Gy. Among groups exposed to a dose split into 0.05 and 0.5 Gy, and single doses of 0.5 and 0.55 Gy, there was no significant difference in incidence of the malformation. The present findings suggest that mouse embryos are not adapted to X-irradiation, but become more susceptible following a low-dose exposure.

Abnormalities, Radiation-Induced↗
PubMed1981

Concanavalin A binding of alpha-fetoprotein in amniotic fluid as an aid in the diagnosis of neural tube defects.

Concanavalin A nonreactive alpha-fetoprotein was determined in samples of amniotic fluid from 16 abnormal pregnancies complicated by anencephaly (7), open spina bifida (6), intra-uterine death (1), anencephaly with exomphalos (1), or open spina bifida with exomphalos (1), and in amniotic fluid from 50 normal pregnancies with gestational age between 13 and 24 weeks. In all 16 cases with fetal malformations, the proportion of nonreactive alpha-fetoprotein was significantly decreased (median 5.3%) as compared with amniotic fluid from pregnancies with a normal outcome (median 39.7%). The results confirm that this measurement is useful in the diagnosis of neural tube defects, especially when the concentration of alpha-fetoprotein in amniotic fluid is normal or only slightly above normal and gestational age is uncertain.

Amniotic Fluid↗
PubMed1999

Maternal periconceptional use of electric bed-heating devices and risk for neural tube defects and orofacial clefts.

Electric and magnetic fields are of concern as risk factors for adverse reproductive outcomes, including congenital anomalies. Among residential exposures to electric and magnetic fields, electric bed-heating devices such as electric blankets may be a substantial source of such exposures, and their use is fairly common. Two population-based case-control studies were analyzed to investigate whether the periconceptional use of electric blankets, bed warmers, or electrically heated waterbeds increased the risk of women to deliver infants or fetuses with neural tube defects (NTDs) or orofacial clefts. We obtained information on bed-heating devices from 538 NTD cases and their 539 controls in one study, and 265 NTD cases and 481 controls and 652 orofacial cleft cases and their 734 controls from another study. Our results revealed a few modestly elevated risks of certain anomaly phenotypes with maternal use of certain bed-heating devices, but risks tended to be imprecise. In general, women who reported more frequent use of a bed-heating device, or longer duration of use, did not appear to have a higher risk for delivering offspring with anomalies than were women who reported less frequent or shorter-duration use.

Electromagnetic Fields↗
PubMed1976

Prenatal diagnosis of neural tube defects. II. Analysis of false positive and false negative alpha-fetoprotein results.

Certain problems and pitfalls attend the use of the alpha-fetoprotein (AFP) assay for the prenatal diagnosis of neural tube defects (NTDs). Analysis of 2495 consecutive cases revealed 57 (2.3%) with amniotic fluid AFP levels greater than 3 SD above the mean. Fetal deaths (9), various fetal abnormalities, (7) and spontaneous abortions (4) occurred among this group. In addition, there were 30 cases with AFP levels greater than + 3 SD above the mean in which a normal child was delivered--a true false positive rate of 1.2%. To determine if the false positive rate could be diminished, 40 amniotic fluid samples with AFP greater than + 2 SD were subjected to further detailed analysis for fetal hemoglobin, total protein, and IgM concentrations. Even with this battery of tests, we estimate that between 1 and 2% of normal amniotic fluids have elevated AFP levels and either fall as expected outside the + 3 SD range, or have elevated AFP levels due to unknown causes.

Amniocentesis↗
PubMed1980

Prenatal diagnosis of neural tube defects. IV. Maternal serum alpha-fetoprotein screening.

The maternal serum alpha-fetoprotein (AFP) in 6161 women in routine pregnancy [2771 in a hospital obstetric clinic (group 1) and 3390 in private practices (group 2)] was studied. Group 1 studies enabled the delineation of the normal range of serum AFP, whereas group 2 represented a true screening experience. In group 2, 39 (2.5%) of 1566 women at 16 to 18 weeks' gestation had raised (2.5 times the median or more) serum AFP. Of these 39 women, 3 (7.8%) had neural tube defects (NTDs), 6 (15.4%) had multiple pregnancies, 1 (2.6%) had congenital nephrosis, 7 (17.9%) had spontaneous abortions, 7 (17.9%) had miscellaneous associated factors, and 15 (38.5%) had raised serum AFP for no obvious reason. Only 16 (1%) women had "unnecessary" amniocenteses. None of these aborted subsequently. Analysis of the combined data showed that NTDs were detectable in 87.5% of patients-all 6 with anencephaly and 1 of 2 with spina bifida (1 spina bifida lesion closed); multiple pregnancy was determined in 45% (18/40 cases), and spontaneous abortion ensued in 14.5%. In group 1 a raised serum AFP was associated with a host of complications in 77.3% of the women. Low AFP values had associated complications in 72.2% of cases. Maternal serum AFP screening represents another potentially important tool for early detection of high-risk pregnancy.

Amniocentesis↗
PubMed1987

Prenatal diagnosis of neural tube defects by measurement of serum alpha-fetoprotein in Havana City.

Prenatal screening was carried out in Havana City, Cuba, as part of a National Medical Genetics Programme, in order to detect elevated alpha-fetoprotein concentration in maternal serum (MS-AFP). A total of 97,900 pregnant women between 15 and 19 weeks of pregnancy were tested from 1982 to 1985. A double-antibody-sandwich technique was used. 173 malformed fetuses were detected. Confirmation was by ultrasonography, elevated AFP values in a second serum sample and in amniotic fluid and acetylcholinesterase. No termination of a normal pregnancy occurred. The screening of all pregnancies is easy, economical and useful for detecting not only fetuses suffering from open Neural Tube Defects (NTDs) and other severe disorders but also pregnancies at risk of further complications.

Acetylcholinesterase↗
PubMed1998

Myelomeningocele and Waardenburg syndrome (type 3) in patients with interstitial deletions of 2q35 and the PAX3 gene: possible digenic inheritance of a neural tube defect.

From a spina bifida clinic we have identified two patients with a syndrome of myelomeningocele and Waardenburg syndrome type 3 (WS3). The patients each possess a single, de novo, interstitial deletion of chromosome 2 (2q35-36.2), including the PAX3 gene. Deletion of PAX3 was confirmed by fluorescence in situ hybridization (FISH). Analysis with PAX3 and flanking microsatellites shows that the deleted interval of chromosome 2 is of paternal origin and is at least 2 and 6 cM in the two patients. Interstitial deletions in this region result in the Waardenburg syndrome (WS1), but have not been associated with neural tube defects (NTDs). Although other etiologies have not been formally excluded, these patients raise the possibility of a digenic etiology of their NTDs via a genetic interaction of the deleted PAX3 gene with a second unidentified locus.

Child, Preschool↗
PubMed1983

Neural tube defects in the Cape Town area, 1975-1980.

During the period 1975-1980, 105 infants out of a total of 116 859 delivered at selected hospitals in the Cape Town area had a neural tube defect. The combined incidence of spina bifida and anencephaly in Whites was approximately 1/300 births, which is similar to that generally encountered in the UK. However, the incidence in other ethnic groups was appreciably lower at 1/1250 and 1/2000 births for the Coloured (mixed ancestry) and Black groups respectively.

Anencephaly↗
PubMedDate not supplied

Peptide-mediated protection from ethanol-induced neural tube defects.

Ethanol inhibition of L1-mediated cell adhesion may contribute to the spectrum of neurological, behavioral and morphological abnormalities associated with prenatal ethanol exposure. We showed previously that the neuroprotective peptides NAPVSIPQ (NAP) and SALLRSIPA (SAL) antagonize ethanol inhibition of L1 adhesion and prevent ethanol-induced growth retardation in mouse whole embryo culture. Here we ask whether NAP and SAL also prevent ethanol-induced major malformations of the nervous system. Gestational day 8.0 (3-5 somites) C57BL/6J mouse embryos were grown for 6 h in control medium, 100 mM ethanol and 10(-10) M peptides and then maintained for an additional 20 h in control medium. At the end of the culture period, only embryos having 18-19 somite pairs were examined and compared for the degree of neural tube closure. Ethanol exposure resulted in neural tube defects (NTDs) consistent with total dysraphia and anencephaly. Co-incubation with ethanol and L-NAP (all L-amino acids), D-NAP (all D-amino acids) or SAL significantly increased the percentage of embryos that had begun to close their neural folds at the level of the forebrain/midbrain junction or that had progressed beyond this stage of closure. P7A-NAP (NAPVSIAQ), which lacks neuroprotective activity, but retains activity as an antagonist of ethanol inhibition of L1 adhesion, was effective in preventing ethanol-induced NTDs. In contrast, I6A-NAP (NAPVSAPQ), which shows reduced efficacy as an ethanol antagonist but retains its neuroprotective efficacy, did not significantly diminish the induction of NTDs by ethanol. These findings demonstrate the ability of NAP and SAL to prevent ethanol-induced NTDs and support the hypothesis that ethanol teratogenesis is caused in part by ethanol inhibition of L1-mediated cell adhesion.

Animals↗