Nocturnal masseter electromyographic activity of complete denture wearers

doi: 10.1111/j.1741‐2358.2011.00528.x Nocturnal masseter electromyographic activity of complete denture wearers Objective: Collection of normative data on activity patterns of the masseter during sleep in elderly denture wearers by portable electromyography (EMG) recorders. Background: Complete denture wearers might suffer from orofacial pain caused by myoarthropathies of the masticatory system. Indeed, denture instability may precipitate parafunctional habits and consequently muscle soreness and/or temporomandibular pain. Materials and methods: We collected normative masseter EMG data during sleep in 15 complete denture wearers (five women, 10 men, 56–88 years) by portable recorders in their natural environment. Activity periods (AP) were signal portions including subthreshold intervals ≤5 s. Signal amplitude was expressed in per cent of maximum voluntary contraction (%MVC). For this reason, maximum bite force was assessed. Twenty age‐matched dentate controls were also recorded for the maximum bite force. Results: We found 157.2 ± 86.5 AP per night, i.e. 24.0 ± 12.2 AP/h. Mean amplitude was 15.1 ± 4.3%MVC. AP lasted 6.8 ± 4.1 s, and their time integral was 126.3 ± 112.5%MVC?s. Maximum bite force was 116.8 ± 69.6 N in the edentulous, significantly lower than in controls (344.8 ± 150.4 N). Conclusions: Healthy complete denture wearers showed intermittent periods of nocturnal masseter activity of very low intensity and short duration.     

Genetic and molecular characterization reveals a unique nucleobase cation symporter 1 in Arabidopsis

Locus At5g03555 encodes a nucleobase cation symporter 1 (AtNCS1) in the Arabidopsis genome. Arabidopsis insertion mutants, AtNcs1-1 and AtNcs1-3, were used for in planta toxic nucleobase analog growth studies and radio-labeled nucleobase uptake assays to characterize solute transport specificities. These results correlate with similar growth and uptake studies of AtNCS1 expressed in Saccharomyces cerevisiae. Both in planta and heterologous expression studies in yeast revealed a unique solute transport profile for AtNCS1 in moving adenine, guanine and uracil. This is in stark contrast to the canonical transport profiles determined for the well-characterized S. cerevisiae NCS1 proteins FUR4 (uracil transport) or FCY2 (adenine, guanine, and cytosine transport).     

Biosynthesis of calystegines: 15N NMR and kinetics of formation in root cultures of Calystegia sepium

Calystegines are nortropane alkaloids bearing between three and five hydroxyl groups in various positions. [15N]Tropinone was administered to root cultures of Calystegia sepium and the incorporation into calystegines was followed. Increase of label in calystegines was measured by one-dimensional 15N NMR and inverse-detected 2D NMR techniques. The results show that tropinone and pseudotropine are metabolites in the biosynthetic pathway of calystegines. The velocity of calystegine accumulation was followed kinetically by transfer of root cultures from 15N-enriched medium to 14N-medium and analysis by GC-MS. A constant calystegine formation with no interference by excretion or degradation was observed. A biosynthetic rate for individual calystegines at each time point was calculated, the maximum was 0.4 mg/day/g of biomass. This allowed the velocity of individual biosynthetic steps to be estimated.     

The Prognostic Value of the Work Ability Index for Sickness Absence among Office Workers

BackgroundThe work ability index (WAI) is a frequently used tool in occupational health to identify workers at risk for a reduced work performance and for work-related disability. However, information about the prognostic value of the WAI to identify workers at risk for sickness absence is scarce.ObjectivesTo investigate the prognostic value of the WAI for sickness absence, and whether the discriminative ability differs across demographic subgroups.MethodsAt baseline, the WAI (score 7-49) was assessed among 1,331 office workers from a Dutch financial service company. Sickness absence was registered during 12-months follow-up and categorised as 0 days, 0<days<5, 5≤days<15, and ≥15 days in one year. Associations between WAI and sickness absence were estimated by multinomial regression analyses. Discriminative ability of the WAI was assessed by the Area Under the Curve (AUC) and Ordinal c-index (ORC). Test characteristics were determined for dichotomised outcomes. Additional analyses were performed for separate WAI dimensions, and subgroup analyses for demographic groups.ResultsA lower WAI was associated with sickness absence (≥15 days vs. 0 days: per point lower WAI score OR=1.27; 95%CI 1.21-1.33). The WAI showed reasonable ability to discriminate between categories of sickness absence (ORC=0.65; 95%CI 0.63-0.68). Highest discrimination was found for comparing workers with ≥15 sick days with 0 sick days (AUC=0.77) or with 1-5 sick days (AUC=0.69). At the cut-off for poor work ability (WAI≤27) the sensitivity to identify workers at risk for ≥15 sick days was 7.5%, the specificity 99.6%, and the positive predictive value 82%. The performance was similar across demographic subgroups.ConclusionsThe WAI could be used to identify workers at high risk for prolonged sickness absence. However, due to low sensitivity many workers will be missed. Hence, additional factors are required to better identify workers at highest risk.     

Smog nitrogen and the rapid acidification of forest soil, San Bernardino Mountains, southern California

We report the rapid acidification of forest soils in the San Bernardino Mountains of southern California. After 30 years, soil to a depth of 25 cm has decreased from a pH (measured in 0.01 M CaCl2) of 4.8 to 3.1. At the 50-cm depth, it has changed from a pH of 4.8 to 4.2. We attribute this rapid change in soil reactivity to very high rates of anthropogenic atmospheric nitrogen (N) added to the soil surface (72 kg ha(-1) year(-1)) from wet, dry, and fog deposition under a Mediterranean climate. Our research suggests that a soil textural discontinuity, related to a buried ancient landsurface, contributes to this rapid acidification by controlling the spatial and temporal movement of precipitation into the landsurface. As a result, the depth to which dissolved anthropogenic N as nitrate (NO3) is leached early in the winter wet season is limited to within the top approximately 130 cm of soil where it accumulates and increases soil acidity.     

Temperature-dependent sex-biased embryo mortality in a bird

Sex ratios have important evolutionary consequences and are often biased by environmental factors. The effect of developmental temperature on offspring sex ratios has been widely documented across a diverse range of taxa but has rarely been investigated in birds and mammals. However, recent field observations and artificial incubation experiments have demonstrated that the hatching sex ratio of a megapode, the Australian brush-turkey (Alectura lathami), varied with incubation temperature; more females hatched at high incubation temperatures and more males hatched at low temperatures. Here, we investigated the causes of this temperature-dependent sex-biasing system. Molecular sexing of chicks and embryos confirmed that male embryo mortality was greater at high temperatures while female embryo mortality is greater at low temperatures, with mortality in both sexes similar at intermediate incubation temperatures. Temperature-dependent sex-biased embryo mortality represents a novel mechanism of altering sex ratios in birds. This novel mechanism, coupled with the unique breeding biology of the brush-turkey, offers a potentially unparalleled opportunity in which to investigate sex allocation theory in birds.     

The common marmoset (Callithrix jacchus) has two very similar semenogelin genes as the result of gene conversion

The semen coagulum proteins have undergone substantial structural changes during evolution. In primates, these seminal vesicle-secreted proteins are known as semenogelin I (SEMG1) and semenogelin II (SEMG2). Previous studies on the common marmoset (Callithrix jacchus) showed that ejaculated semen from this New World monkey contains semenogelin, but it remained unclear whether it carries both genes or only SEMG1 and no SEMG2, like the closely related cotton-top tamarin (Saguinus oedipus). In this study we show that there are two genes, both expressed in the seminal vesicles. Surprisingly, the genes show an almost perfect sequence identity in a region of 1.25 kb, encompassing nearly half of the genes and containing exon 1, intron 1, and the first 0.9 kb of exon 2. The underlying molecular mechanism is most likely gene conversion, and a phylogenetic analysis suggests that SEMG1 is the most probable donor gene. The marmoset SEMG1 in this report differs from a previously reported cDNA by a lack of nucleotides encoding one repeat of 60 amino acids, suggesting that marmoset SEMG1 displays allelic size variation. This is similar to what was recently demonstrated in humans, but in marmosets the polymorphism was generated by a repeat duplication, whereas in humans it was a deletion. Together, these studies shed new light on the evolution of semenogelins and the mechanisms that have generated the structural diversity of semen coagulum proteins.