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.

Folate status and homocysteine response to folic acid doses and withdrawal among young Chinese women in a large-scale randomized double-blind trial

BACKGROUND

There are no large randomized trials of the effect of folic acid dosing regimens on blood folate and homocysteine concentrations.

OBJECTIVE

We aimed to evaluate the changes in folate and homocysteine concentrations in response to different folic acid doses and to withdrawal in young women not exposed to other sources of folic acid.

DESIGN

Women (n = 1108) were randomly assigned to 1 of 6 intervention groups for which daily intakes of folic acid for 6 mo were 100 microg 1 time/d, 25 microg 4 times/d, 400 microg 1 time/d, 100 microg 4 times/d, 4000 microg 1 time/d, or 4000 microg 1 time/wk. Plasma and red blood cell folate and homocysteine concentrations were measured at baseline; at 1, 3, and 6 mo; and 3 mo after the discontinuation of folic acid.

RESULTS

Folate and homocysteine concentrations were not different at baseline between the groups who had the same daily intake of folic acid as a single dose or multiple doses (P = 0.058). Plasma folate concentrations plateaued at 3 mo with 108% (95% CI: 97.7%, 120%), 259% (95% CI: 240%, 279%), 460% (95% CI: 417%, 503%), and 142% (95% CI: 123%, 162%) observed increases for the folic acid groups receiving 100, 400, and 4000 microg/d and 4000 microg/wk, respectively. The rate of reduction in folate concentrations during the 3 mo after cessation of folic acid was dose-dependent-higher intakes were associated with faster reductions.

CONCLUSIONS

Changes in folate and homocysteine concentrations were unaffected by different dosing schedules. After folic acid cessation, blood folate declined rapidly, which indicated that the intervention-enhanced folate status was rapidly diminished.

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.

Improvement in stroke mortality in Canada and the United States, 1990 to 2002

BACKGROUND

In the United States and Canada, folic acid fortification of enriched grain products was fully implemented by 1998. The resulting population-wide reduction in blood homocysteine concentrations might be expected to reduce stroke mortality if high homocysteine levels are an independent risk factor for stroke.

METHODS AND RESULTS

In this population-based cohort study with quasi-experimental intervention, we used segmented log-linear regression to evaluate trends in stroke-related mortality before and after folic acid fortification in the United States and Canada and, as a comparison, during the same period in England and Wales, where fortification is not required. Average blood folate concentrations increased and homocysteine concentrations decreased in the United States after fortification. The ongoing decline in stroke mortality observed in the United States between 1990 and 1997 accelerated in 1998 to 2002 in nearly all population strata, with an overall change from -0.3% (95% CI, -0.7 to 0.08) to -2.9 (95% CI, -3.5 to -2.3) per year (P=0.0005). Sensitivity analyses indicate that changes in other major recognized risk factors are unlikely to account for the reduced number of stroke-related deaths in the United States. The fall in stroke mortality in Canada averaged -1.0% (95% CI, -1.4 to -0.6) per year from 1990 to 1997 and accelerated to -5.4% (95% CI, -6.0 to -4.7) per year in 1998 to 2002 (P< or =0.0001). In contrast, the decline in stroke mortality in England and Wales did not change significantly between 1990 and 2002.

CONCLUSIONS

The improvement in stroke mortality observed after folic acid fortification in the United States and Canada but not in England and Wales is consistent with the hypothesis that folic acid fortification helps to reduce deaths from stroke.

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.

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.

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, <or=200 d in milk (DIM) vs. >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 <or=200 DIM (n = 17) than for cows (n = 15) in late lactation (25.5 +/- 1.3 vs. 21.0 degrees C). The DeltaT was also greater for cows <or=200 DIM compared with those >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 <or=200 DIM compared with those in late lactation. In contrast, underrun heel was more frequently observed among 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 <or=200 DIM compared with cows later in lactation, measurement of hoof temperatures among cows in early lactation may be useful in monitoring hoof health.