Twinning and major birth defects, National Birth Defects Prevention Study, 1997-2007.

BACKGROUND: Twinning has been associated with many types of birth defects, although previous studies have had inconsistent findings. Many studies lack information about potential confounders, particularly use of fertility treatment. Our objective was to assess the association between twinning and birth defects in the National Birth Defects Prevention Study (NBDPS). METHODS: We used data from the NBDPS, a population-based, case-control study of major birth defects in the USA, to evaluate associations between twinning and birth defects. The study population included mothers of twin and singleton controls (live-born infants without major birth defects), and cases (fetuses or infants with a major birth defect) born October 1997-December 2007. Adjusted ORs and 95% CIs were estimated using multivariable logistic regression stratified by use of fertility treatment. Twin sex-pairing data and a simulation approach were used to estimate the zygosity of twins. RESULTS: In the unassisted conception stratum, we observed significant positive associations between twinning and 29 of 45 defect groups. The largest effect estimates were observed for multiple ventricular septal defects and cloacal exstrophy. Among mothers reporting any use of fertility treatments, we observed a significant association with twinning for 5 of 25 defect groups, with the largest effect estimates for hypoplastic left heart syndrome and omphalocele. OR estimates in the estimated monozygotic stratum were generally further from the null than in the dizygotic stratum. CONCLUSIONS: Compared with singletons, a wide range of birth defects are significantly more common among twins. Birth defect risk in twins may be differential by use of fertility treatment.

Optimal serum and red blood cell folate concentrations in women of reproductive age for prevention of neural tube defects: World Health Organization guidelines.

Neural tube defects (NTDs) such as spina bifida, anencephaly, and encephalocele are serious birth defects of the brain and spine that occur during the first month of pregnancy when the neural tube fails to close completely. Randomized controlled trials and observational studies have shown that adequate daily consumption of folic acid before and during early pregnancy considerably reduces the risk for NTDs. The U.S. Public Health Service recommends that women capable of becoming pregnant consume 400 µg of folic acid daily for NTD prevention. Furthermore, fortification of staple foods (e.g., wheat flour) with folic acid has decreased folate-sensitive NTD prevalence in multiple settings and is a highly cost-effective intervention.

Folate status and concentrations of serum folate forms in the US population: National Health and Nutrition Examination Survey 2011-2.

Serum and erythrocyte (RBC) total folate are indicators of folate status. No nationally representative population data exist for folate forms. We measured the serum folate forms (5-methyltetrahydrofolate (5-methylTHF), unmetabolised folic acid (UMFA), non-methyl folate (sum of tetrahydrofolate (THF), 5-formyltetrahydrofolate (5-formylTHF), 5,10-methenyltetrahydrofolate (5,10-methenylTHF)) and MeFox (5-methylTHF oxidation product)) by HPLC-MS/MS and RBC total folate by microbiologic assay in US population ≥ 1 year (n approximately 7500) participating in the National Health and Nutrition Examination Survey 2011-2. Data analysis for serum total folate was conducted including and excluding MeFox. Concentrations (geometric mean; detection rate) of 5-methylTHF (37·5 nmol/l; 100 %), UMFA (1·21 nmol/l; 99·9 %), MeFox (1·53 nmol/l; 98·8 %), and THF (1·01 nmol/l; 85·2 %) were mostly detectable. 5-FormylTHF (3·6 %) and 5,10-methenylTHF (4·4 %) were rarely detected. The biggest contributor to serum total folate was 5-methylTHF (86·7 %); UMFA (4·0 %), non-methyl folate (4·7 %) and MeFox (4·5 %) contributed smaller amounts. Age was positively related to MeFox, but showed a U-shaped pattern for other folates. We generally noted sex and race/ethnic biomarker differences and weak (Spearman's r< 0·4) but significant (P< 0·05) correlations with physiological and lifestyle variables. Fasting, kidney function, smoking and alcohol intake showed negative associations. BMI and body surface area showed positive associations with MeFox but negative associations with other folates. All biomarkers showed significantly higher concentrations with recent folic acid-containing dietary supplement use. These first-time population data for serum folate forms generally show similar associations with demographic, physiological and lifestyle variables as serum total folate. Patterns observed for MeFox may suggest altered folate metabolism dependent on biological characteristics.

Hypomethylation of serum blood clot DNA, but not plasma EDTA-blood cell pellet DNA, from vitamin B12-deficient subjects.

Vitamin B12, a co-factor in methyl-group transfer, is important in maintaining DNA (deoxycytidine) methylation. Using two independent assays we examined the effect of vitamin B12-deficiency (plasma vitamin B12<148 pmol/L) on DNA methylation in women of childbearing age. Coagulated blood clot DNA from vitamin B12-deficient women had significantly (p<0.001) lower percentage deoxycytidine methylation (3.23±0.66%; n = 248) and greater [3 H]methyl-acceptance (42,859±9,699 cpm; n = 17) than DNA from B12-replete women (4.44±0.18%; n = 128 and 26,049±2,814 cpm; n = 11) [correlation between assays: r = -0.8538; p<0.001; n = 28]. In contrast, uncoagulated EDTA-blood cell pellet DNA from vitamin B12-deficient and B12-replete women exhibited similar percentage methylation (4.45±0.15%; n = 77 vs. 4.47±0.15%; n = 47) and [3 H]methyl-acceptance (27,378±4,094 cpm; n = 17 vs. 26,610±2,292 cpm; n = 11). Therefore, in simultaneously collected paired blood samples, vitamin B12-deficiency was associated with decreased DNA methylation only in coagulated samples. These findings highlight the importance of sample collection methods in epigenetic studies, and the potential impact biological processes can have on DNA methylation during collection.

Modeling fortification of corn masa flour with folic acid: the potential impact on exceeding the tolerable upper intake level for folic acid, NHANES 2001-2008.

BACKGROUND: The Institute of Medicine set a tolerable upper intake level (UL) for usual daily total folic acid intake (1,000 µg). Less than 3% of US adults currently exceed the UL. OBJECTIVE: The objective of this study was to determine if folic acid fortification of corn masa flour would increase the percentage of the US population who exceed the UL. DESIGN: We used dietary intake data from NHANES 2001-2008 to estimate the percentage of adults and children who would exceed the UL if corn masa flour were fortified at 140 µg of folic acid/100 g. RESULTS: In 2001-2008, 2.5% of the US adult population (aged≥19 years) exceeded the UL, which could increase to 2.6% if fortification of corn masa flour occurred. With corn masa flour fortification, percentage point increases were small and not statistically significant for US adults exceeding the UL regardless of supplement use, sex, race/ethnicity, or age. Children aged 1-8 years, specifically supplement users, were the most likely to exceed their age-specific UL. With fortification of corn masa flour, there were no statistically significant increases in the percentage of US children who were exceeding their age-specific UL, and the percentage point increases were small. CONCLUSIONS: Our results suggest that fortification of corn masa flour would not significantly increase the percentage of individuals who would exceed the UL. Supplement use was the main factor related to exceeding the UL with or without fortification of corn masa flour and within all strata of sex, race/ethnicity, and age group.

Estimation of trends in serum and RBC folate in the U.S. population from pre- to postfortification using assay-adjusted data from the NHANES 1988-2010.

The NHANES has monitored folate status of the U.S. population from prefortification (1988-1994) to postfortification (1999-2010) by measuring serum and RBC folate concentrations. The Bio-Rad radioassay (BR) was used from 1988 to 2006, and the microbiologic assay (MBA) was used from 2007 to 2010. The MBA produces higher concentrations than the BR and is considered to be more accurate. Thus, to bridge assay differences and to examine folate trends over time, we adjusted the BR results to be comparable to the MBA results. Postfortification, assay-adjusted serum and RBC folate concentrations were 2.5 times and 1.5 times prefortification concentrations, respectively, and showed a significant linear trend (P < 0.001) to slightly lower concentrations during 1999-2010. The postfortification prevalence of low serum (<10 nmol/L) or RBC (<340 nmol/L) folate concentrations was ≤ 1%, regardless of demographic subgroup, compared with 24% for serum folate and 3.5% for RBC folate prefortification, with substantial variation among demographic subgroups. The central 95% reference intervals for serum and RBC folate varied by demographic subgroup during both pre- and postfortification periods. Age and dietary supplement use had the greatest effects on prevalence estimates of low folate concentrations during the prefortification period. In summary, the MBA-equivalent blood folate concentrations in the U.S. population showed first a sharp increase from pre- to postfortification, then showed a slight decrease (17% for serum and 12% for RBC folate) during the 12-y postfortification period. The MBA-equivalent pre- and postfortification reference concentrations will inform countries that plan folic acid fortification or that need to evaluate its impact.

Iron, folate, and B(12) deficiencies and their associations with anemia among women of childbearing age in a rural area in Northern China.

OBJECTIVE: To assess the prevalence of folate, vitamin B(12), and iron deficiencies and their associations with anemia among women of childbearing age in northern China, an area with a reported high incidence of neural tube defects. METHODS: Plasma folate, vitamin B(12), ferritin, and hemoglobin levels were measured among 1,671 non-pregnant women of childbearing age from Xianghe County, Hebei Province, China in June 2004. RESULTS: Geometric means [95 % confidence interval (CI)] of plasma concentrations were 9.3 (4.0, 21.6) nmol/L for folate, 213.1 (82.4, 550.9) pmol/L for vitamin B(12), 17.4 (1.1, 278.6) microg/L for ferritin, and 129.9 (104.6, 161.4) g/L for hemoglobin (Hb). Approximately 24 % of women had biochemical evidence of folate deficiency (<6.8 nmol/L), 21.4 % were deficient (<148 pmol/L) in vitamin B(12), 30.2 % had iron depletion (<15 microg/L), and anemia (Hb < 120 g/L) was detected among 15.4 % of women. Of the three nutrients, only iron depletion (ferritin < 15 microg/L) was independently associated with anemia (adjusted odds ratio = 6.4, 95 % CI 4.8, 8.6). CONCLUSIONS: Although there were substantial proportions of folate and vitamin B(12) deficiencies among women of childbearing age in northern China, iron deficiency was the most important contributor to anemia.

Evolution rampant: house mice on Madeira.

House mice are extra-ordinary animals -extra-ordinary in the literal sense of that word. They are pests - but also a valued laboratory animal. They are generalized rodents - and successful in habitats from tundra to tropics and from sea-level to high altitudes. They have differentiated into a perplexity of taxa, yet differ little in their general morphology. They were long scorned by ecologists as recently arrived commensals, but are increasingly illuminating evolutionary processes as new techniques are applied to their study. Local forms, once valued only by taxonomists, are proving ever more interesting as their genetics are probed. In 1992, Mathias & Mira described the apparently unexciting characteristics of mice living on the two main islands of the Madeira group, 600 km west of continental Portugal. Then in 2000, Britton-Davidian et al. discovered that there were at least six chromosomal (Robertsonian) races on the main island. In the past decade, studies of molecular and mitochondrial genomes have shown an array of variables and posed questions about the origins and subsequent evolution of these island mice. In this issue of Molecular Ecology, Förster et al. report on the mtDNA haplotypes found on the island and in mainland Portugal, discuss the probable source of the island colonizers, and consider data which might give information about the timing of the colonizing event(s).

Of mice and (Viking?) men: phylogeography of British and Irish house mice.

The west European subspecies of house mouse (Mus musculus domesticus) has gained much of its current widespread distribution through commensalism with humans. This means that the phylogeography of M. m. domesticus should reflect patterns of human movements. We studied restriction fragment length polymorphism (RFLP) and DNA sequence variations in mouse mitochondrial (mt) DNA throughout the British Isles (328 mice from 105 localities, including previously published data). There is a major mtDNA lineage revealed by both RFLP and sequence analyses, which is restricted to the northern and western peripheries of the British Isles, and also occurs in Norway. This distribution of the 'Orkney' lineage fits well with the sphere of influence of the Norwegian Vikings and was probably generated through inadvertent transport by them. To form viable populations, house mice would have required large human settlements such as the Norwegian Vikings founded. The other parts of the British Isles (essentially most of mainland Britain) are characterized by house mice with different mtDNA sequences, some of which are also found in Germany, and which probably reflect both Iron Age movements of people and mice and earlier development of large human settlements. MtDNA studies on house mice have the potential to reveal novel aspects of human history.

Review of interventions for the prevention and control of folate and vitamin B12 deficiencies.

Folate and vitamin B12 deficiencies represent important and evolving global health challenges that contribute to the global burden of anemia, neurologic conditions, neurodevelopmental disorders, and birth defects. We present a review of population-based programs designed to increase consumption of folates and vitamin B12. A folic acid supplementation program targeting couples prior to marriage in China has led to optimal consumption of supplements containing folic acid and a significant reduction of neural tube defects (NTD). Supplementation programs that use mass community education show some promise, but have not been shown to be as effective as targeted education. The success of supplementation programs hinges on a strong and persistent educational component and access to the supplements. Fortification with folic acid has been shown to reduce the prevalence of NTD in the countries where it has been implemented. Challenges to fortification programs include identifying the appropriate delivery vehicles, setting the optimal fortification level, sustaining the quality assurance of the fortification level, and addressing regulatory challenges and trade barriers of commercially fortified flours. Supplementation and fortification are cost-effective and viable approaches to reducing the burden of NTD, anemia, and other conditions resulting from folate deficiency. The experience with interventions involving folic acid could provide a model for the subsequent development of supplementation and fortification programs involving vitamin B12.

Race-ethnicity differences in folic acid intake in women of childbearing age in the United States after folic acid fortification: findings from the National Health and Nutrition Examination Survey, 2001-2002.

BACKGROUND: Neural tube defects are serious birth defects of the brain and spinal cord. Up to 70% of neural tube defects can be prevented by the consumption of folic acid by women before and early during pregnancy. OBJECTIVE: The objective was to examine folic acid intake in women of childbearing age in the United States. DESIGN: We analyzed nutrient intake data reported by 1685 nonpregnant women aged 15-49 y who participated in the National Health and Nutritional Examination Survey, 2001-2002. RESULTS: The adjusted geometric mean consumption of folic acid from fortified foods was 128 microg/d (95% CI: 123, 134 microg/d) in nonpregnant women. Eight percent (95% CI: 5.8%, 11.0%) of nonpregnant women reported consuming >or=400 microg folic acid/d from fortified foods. This proportion was lower among non-Hispanic black women (5.0%) than among non-Hispanic white (8.9%) or Hispanic (6.8%) women. A smaller percentage of non-Hispanic black (19.1%) and Hispanic (21%) women than of non-Hispanic white women (40.5%) consumed >or=400 microg folic acid from supplements, fortified foods, or both, in addition to food folate, as recommended by the Institute of Medicine to reduce the frequency of neural tube defects. CONCLUSIONS: Most nonpregnant women of childbearing age in the United States reported consuming less than the recommended amount of folic acid. The proportion with low daily folic acid intake was significantly higher in non-Hispanic black and Hispanic women than in non-Hispanic white women. At the present level of folic acid fortification, most women need to take a folic acid-containing dietary supplement to achieve the Institute of Medicine recommendation.

Plasma melatonin and insulin-like growth factor-1 responses to dim light at night in dairy heifers.

The effect of dim (5, 10 and 50 1x) light at night on night plasma melatonin level (NML) and night plasma insulin-like growth factor-1 (IGF-1) level was determined in 12 prepubertal Holstein heifers (245 +/- 16 days age) using a 4 x 4 Latin Square design with 14-day treatment and 14-day recovery periods. Blood samples were collected at 23:00 hr (prior to the 8 hr night treatment which commenced at mid-night) on days 0, 3 and 13, and throughout the night at 01:00, 02:00, 03:00, 04:00, 06:00 and 08:00 hr on days 1, 4 and 14 of treatment. Plasma was analysed by radioimmunoassay for melatonin (all samples) and IGF-1 (samples for day 14, 04:00 hr only). Treatment (P = 0.03) and treatment x time (P = 0.02) were significant for NML. Exposure to 50 lx suppressed NML by 50% during the initial 2 hr of the night, but not thereafter. Exposure to 5 and 10 lx had no effect on NML. The NML response to 50 lx was found on all treatment days studied (treatment x time x day; P = 0.99). There was no treatment effect on plasma IGF-1 level (P = 0.89), but plasma IGF-1 level was higher (P = 0.001) during period 4. Plasma IGF-1 level and NML tended (P = 0.10) to be negatively correlated. Light intensities of 10 lx or less appear safe for use at night in dairy barns where darkness is recommended.

Molecular dynamics study of translational and rotational diffusion in liquid ortho-terphenyl.

NVT molecular dynamics simulations were performed on liquid o-terphenyl as a function of temperature in the range 320-480 K. Computed translational diffusion coefficients displayed the non-Arrhenius behavior expected of a fragile glass-forming liquid and were in good, semiquantitative agreement with experimental results. Rotational correlation functions calculated for various vectors within the molecule exhibited a very short time (0-1 ps) initial decay, followed by a reversal, which corresponds to free reorientation within the "solvent" cage prior to collision with a wall. Rotational correlation times of three orthogonal vectors fixed on the central benzene were close to equal at all temperatures, indicating nearly isotropic overall molecular reorientation. The average correlation times exhibited a non-Arrhenius temperature dependence and were in very good agreement with experimental values derived from 2D and 1H NMR relaxation times. Correlation times of vectors located on the lateral phenyl rings were used to calculate the "spinning" internal rotation diffusion coefficients, which were approximately twice as great as the overall rotational diffusion constants, indicating rapid internal rotation of the phenyl side groups over wide ranges of angle in the liquid.

Short communication: infrared thermography and visual examination of hooves of dairy cows in two stages of lactation.

Hooves of 16 lactating Holstein cows were examined twice for sole hemorrhages and underrun heels. Images of hooves were taken using infrared thermography to determine the temperatures of the coronary band and that of a control area above the coronary band. To adjust for skin (control) temperature, the difference (DeltaT) between the coronary band and the control area was calculated. Effects of stage of lactation, that is, 200 DIM, on temperature of the coronary band, DeltaT, and visual abnormalities were determined. Temperatures of the coronary bands of cows were greater for cows 200 DIM (6.1 +/- 0.8 vs. 3.3 +/- 0.9 degrees C). The DeltaT was greater for lateral claws than for medial claws (5.2 +/- 0.6 vs. 4.2 +/- 0.6 degrees C). Chi-square analysis revealed that the frequency of sole hemorrhages in hind lateral claws was significantly higher for cows 200 DIM. Increased temperatures of the coronary band and DeltaT in early/midlactation coincided with increased incidence of sole hemorrhages, but not to incidences of underrun heels. Because higher hoof temperatures occurred in cows

Impact of misclassification of in vitro fertilisation in studies of folic acid and twinning: modelling using population based Swedish vital records.

OBJECTIVE: To determine whether failure to adequately adjust for a reported 40% misclassification of use of in vitro fertilisation (IVF) as reported in a Swedish study could have led to a false finding that folic acid increases dizygotic twinning. DESIGN: Modelling with population based data. SETTING: Swedish vital records for 1995-9. MAIN OUTCOME MEASURES: Rates of twinning calculated according to whether women used IVF to become pregnant. Estimated unadjusted and adjusted odds ratios of the association between use of folic acid and twinning by use of IVF. RESULTS: In 1995-9, Swedish women who used IVF had an almost 20 times the chance of having twins than women who did not use IVF (rate ratio 19.7, 95% confidence interval 18.7 to 20.6). In the absence of a true effect of folic acid, the use of a 40% misclassified surrogate variable to adjust for use of IVF would have resulted in a false finding that folic acid was associated with a more than twofold increase in twinning. CONCLUSION: Use of IVF is a strong confounder because it is associated with both use of folic acid and twinning. Even when misclassification of IVF was reduced to 5%, this bias persisted in the adjusted model. Using a 40% misclassified surrogate to adjust for IVF, as reported in the Swedish study, probably led to a false finding that folic acid increased dizygotic twinning.

Molecular dynamics study of anisotropic translational and rotational diffusion in liquid benzene.

Equilibrium NPT and NVT molecular dynamics simulations were performed on liquid benzene over an extended range of temperature (from 260 to 360 K) using the COMPASS force field. Densities and enthalpies of vaporization (from cohesive energy densities) were within 1% of experiment at all temperatures. tumbling and spinning rotational diffusion coefficients, D(perpendicular) and D(parallel), computed as a function of temperature, agreed qualitatively with the results of earlier reported experimental and computational investigations. Generally, it was found that D(parallel)/D(perpendicular) approximately 1.4-2.5 and the activation energy for tumbling was significantly greater than for spinning about the C6 axis [Ea(D(perpendicular)) = 8.1 kJ mol(-1) and Ea(D(parallel)) = 4.5 kJ mol(-1)]. Calculated translational diffusion coefficients were found to be in quantitative agreement with experimental values at all temperatures [deviations were less than the scatter between different reported measurements]. In addition, translational diffusion coefficients were computed in the molecule-fixed frame to yield values for Dxy (diffusion in the plane of the molecule) and Dz (diffusion perpendicular to the plane). It was found that the ratio Dxy/Dz approximately 2.0, and that the two coefficients have roughly equal activation energies. This represents the first atomistic molecular dynamics study of translational diffusion in the molecular frame.

A population-based birth defects surveillance system in the People's Republic of China.

We describe a unique birth defects surveillance system in the People's Republic of China. The system was instituted in March 1992 as a component of an evaluation of the effectiveness of a public health campaign using periconceptional folic acid supplementation to prevent neural tube defects, and currently surveys birth cohorts of approximately 150 000 infants per year. Local health care providers collect information in the form of detailed written descriptions and photographs of affected infants. The system allows for detection of birth defects at the local level with later definitive classification and coding; however, information is limited to structural anomalies that are visible on physical examination. This birth defects surveillance system provides an extensive database of infants with major and minor external structural anomalies, including the unique feature of a photographic record for most cases. These data can be used for aetiological studies, descriptive epidemiology and identification of unusual trends.