Mechanistic models of seed dispersal by wind

Over the past century, various mechanistic models have been developed to estimate the magnitude of seed dispersal by wind, and to elucidate the relative importance of physical and biological factors affecting this passive transport process. The conceptual development has progressed from ballistic models, through models incorporating vertically variable mean horizontal windspeed and turbulent excursions, to models accounting for discrepancies between airflow and seed motion. Over hourly timescales, accounting for turbulent fluctuations in the vertical velocity component generally leads to a power-law dispersal kernel that is censored by an exponential cutoff far from the seed source. The parameters of this kernel vary with the flow field inside the canopy and the seed terminal velocity. Over the timescale of a dispersal season, with mean wind statistics derived from an “extreme-value” distribution, these distribution-tail effects are compounded by turbulent diffusion to yield seed dispersal distances that are two to three orders of magnitude longer than the corresponding ballistic models. These findings from analytic models engendered explicit simulations of the effects of turbulence on seed dispersal using computationally intensive fluid dynamics tools. This development marks a bifurcation in the approaches to wind dispersal, seeking either finer resolution of the dispersal mechanism at the scale of a single dispersal event, or mechanistically derived analytical dispersal kernels needed to resolve long-term and large-scale processes such as meta-population dynamics and range expansion. Because seed dispersal by wind is molded by processes operating over multiple scales, new insights will require novel theoretical tactics that blend these two approaches while preserving the key interactions across scales.     

Mutations in ap1b1 Cause Mistargeting of the Na+/K+-ATPase Pump in Sensory Hair Cells

The hair cells of the inner ear are polarized epithelial cells with a specialized structure at the apical surface, the mechanosensitive hair bundle. Mechanotransduction occurs within the hair bundle, whereas synaptic transmission takes place at the basolateral membrane. The molecular basis of the development and maintenance of the apical and basal compartments in sensory hair cells is poorly understood. Here we describe auditory/vestibular mutants isolated from forward genetic screens in zebrafish with lesions in the adaptor protein 1 beta subunit 1 (ap1b1) gene. Ap1b1 is a subunit of the adaptor complex AP-1, which has been implicated in the targeting of basolateral membrane proteins. In ap1b1 mutants we observed that although the overall development of the inner ear and lateral-line organ appeared normal, the sensory epithelium showed progressive signs of degeneration. Mechanically-evoked calcium transients were reduced in mutant hair cells, indicating that mechanotransduction was also compromised. To gain insight into the cellular and molecular defects in ap1b1 mutants, we examined the localization of basolateral membrane proteins in hair cells. We observed that the Na⁺/K⁺-ATPase pump (NKA) was less abundant in the basolateral membrane and was mislocalized to apical bundles in ap1b1 mutant hair cells. Accordingly, intracellular Na⁺ levels were increased in ap1b1 mutant hair cells. Our results suggest that Ap1b1 is essential for maintaining integrity and ion homeostasis in hair cells.     

Gastrointestinal Symptoms are Still Prevalent and Negatively Impact Health-Related Quality of Life: A Large Cross-Sectional Population Based Study in The Netherlands

Background

Over the last decades important risk factors for gastrointestinal symptoms have shifted, which may have changed its population prevalence. The aim of this study was to assess the current prevalence of gastrointestinal symptoms, appraise associated factors and assess health-related quality of life in the general population.

Methods

A total of 51,869 questionnaires were sent to a representative sample of the Dutch adult general population in December 2008. Demographic characteristics, gastrointestinal symptoms, health-related quality of life, medication use and co-morbidity were reported. We used multivariable logistic regression analysis to determine factors associated with gastrointestinal symptoms.

Results

A total of 18,317 questionnaires were returned, and 16,758 were eligible for analysis. Prevalence of gastrointestinal symptoms was 26%. Most frequent symptoms were bloating (63%), borborygmi (60%) and flatulence (71%). Female gender (adjusted OR (aOR) 1.59, 95% CI 1.43–1.77), asthma/COPD (aOR 1.47, 95% CI 1.21–1.79), use of paracetamol (aOR 1.33, 95% CI 1.20–1.47), antidepressants (aOR 1.56, 95% CI 1.22–2.00) and acid-suppressive medication were independently associated with presence of gastrointestinal symptoms. Age over 65 years (aOR 0.75, 95% CI 0.65–0.87), and use of statins (aOR 0.75, 95% CI 0.61–0.93) were associated with a lower prevalence of gastrointestinal symptoms. Respondents with gastrointestinal symptoms had a lower mean health-related quality of life of 0.81 (SD = 0.21) compared to 0.92 (SD = 0.14) for persons without gastrointestinal symptoms (P<0.01).

Conclusions

Prevalence of gastrointestinal symptoms in the Dutch community is high and associated with decreased health-related quality of life.     

The impact of tail tip amputation and ink tattoo on C57BL/6JBomTac mice

Genetic material for polymerase chain reaction (PCR) and Southern blot analysis on transgenic mice is normally obtained by tail biopsy. Additionally, it may be necessary to tattoo the mice, as it is essential to have a good and permanent identification. The aim of this study was to evaluate the effects of amputating the tip of the tail to obtain a biopsy for genetic analysis and of ink tattooing on welfare in C57BL/6J mice, a strain often used as genetic background for transgenes. The behaviour of the animals, fluctuating asymmetry (FA, a measure of developmental instability) and the level of restitution in the remaining part of the tail were evaluated and used for an assessment of the impact of these procedures on the welfare of the animals. One group of mice was marked by tail tattooing at various ages. Another group of mice were tail amputated at 12 or 20 days of age. Body weight and FA were followed, and at the end of the experiment, the level of fear/anxiety was assessed using a light-dark box. In the group of tail-amputated animals observation of climbing behaviour and a beam walking test for balance was performed. Seven weeks after tail amputation, the animals were euthanized. The remaining part of the tail was evaluated histopathologically. Body weight, behaviour in the light-dark box and balance test results were not influenced by tail amputation or tattooing. FA was only transiently increased by tattooing. Climbing behaviour was reduced just after tail amputation at 20 days of age. No signs of neuromas were found in the amputated tails, but seven weeks after amputation a significant number of mice did not have fully regenerated glandular tissue and hair follicles in the tail. It is concluded that both tail amputation and tail tattooing seem to have minor short-term negative effects on welfare and that the tissues on the tail probably do not regenerate fully after amputation.     

MLL fusion-driven activation of CDK6 potentiates proliferation in MLL-rearranged infant ALL

Acute lymphoblastic leukemia in infants (     

Reliability of Contractile Properties of the Knee Extensor Muscles in Individuals with Post-Polio Syndrome

Objective

To assess the reliability of contractile properties of the knee extensor muscles in 23 individuals with post-polio syndrome (PPS) and 18 age-matched healthy individuals.

Methods

Contractile properties of the knee extensors were assessed from repeated electrically evoked contractions on 2 separate days, with the use of a fixed dynamometer. Reliability was determined for fatigue resistance, rate of torque development (MRTD), and early and late relaxation time (RT50 and RT25), using the intraclass correlation coefficient (ICC) and standard error of measurement (SEM, expressed as % of the mean).

Results

In both groups, reliability for fatigue resistance was good, with high ICCs (>0.90) and small SEM values (PPS: 7.1%, healthy individuals: 7.0%). Reliability for contractile speed indices varied, with the best values found for RT50 (ICCs>0.82, SEM values <2.8%). We found no systematic differences between test and retest occasions, except for RT50 in healthy subjects (p = 0.016).

Conclusions

In PPS and healthy individuals, the reliability of fatigue resistance, as obtained from electrically evoked contractions is high. The reliability of contractile speed is only moderate, except for RT50 in PPS, demonstrating high reliability.

Significance

This was the first study to examine the reliability of electrically evoked contractile properties in individuals with PPS. Our results demonstrate its potential to study mechanisms underlying muscle fatigue in PPS and to evaluate changes in contractile properties over time in response to interventions or from natural course.     

Can Multiple Lifestyle Behaviours Be Improved in People with Familial Hypercholesterolemia? Results of a Parallel Randomised Controlled Trial

Objective

To evaluate the efficacy of an individualised tailored lifestyle intervention on physical activity, dietary intake, smoking and compliance to statin therapy in people with Familial Hypercholesterolemia (FH).

Methods

Adults with FH (n = 340) were randomly assigned to a usual care control group or an intervention group. The intervention consisted of web-based tailored lifestyle advice and face-to-face counselling. Physical activity, fat, fruit and vegetable intake, smoking and compliance to statin therapy were self-reported at baseline and after 12 months. Regression analyses were conducted to examine between-group differences. Intervention reach, dose and fidelity were assessed.

Results

In both groups, non-significant improvements in all lifestyle behaviours were found. Post-hoc analyses showed a significant decrease in saturated fat intake among women in the intervention group (β = −1.03; CI −1.98/−0.03). In the intervention group, 95% received a log on account, of which 49% logged on and completed one module. Nearly all participants received face-to-face counselling and on average, 4.2 telephone booster calls. Intervention fidelity was low.

Conclusions

Individually tailored feedback is not superior to no intervention regarding changes in multiple lifestyle behaviours in people with FH. A higher received dose of computer-tailored interventions should be achieved by uplifting the website and reducing the burden of screening questionnaires. Counsellor training should be more extensive.

Trial Registration

Dutch Trial Register NTR1899     

Genetics and molecular basis of human peroxisome biogenesis disorders

Human peroxisome biogenesis disorders (PBDs) are a heterogeneous group of autosomal recessive disorders comprised of two clinically distinct subtypes: the Zellweger syndrome spectrum (ZSS) disorders and rhizomelic chondrodysplasia punctata (RCDP) type 1. PBDs are caused by defects in any of at least 14 different PEX genes, which encode proteins involved in peroxisome assembly and proliferation. Thirteen of these genes are associated with ZSS disorders. The genetic heterogeneity among PBDs and the inability to predict from the biochemical and clinical phenotype of a patient with ZSS which of the currently known 13 PEX genes is defective, has fostered the development of different strategies to identify the causative gene defects. These include PEX cDNA transfection complementation assays followed by sequencing of the thus identified PEX genes, and a PEX gene screen in which the most frequently mutated exons of the different PEX genes are analyzed. The benefits of DNA testing for PBDs include carrier testing of relatives, early prenatal testing or preimplantation genetic diagnosis in families with a recurrence risk for ZSS disorders, and insight in genotype-phenotype correlations, which may eventually assist to improve patient management. In this review we describe the current status of genetic analysis and the molecular basis of PBDs. This article is part of a Special Issue entitled: Metabolic Functions and Biogenesis of peroxisomes in Health and Disease.     

Diversification within grapevine cultivars goes through chimeric states.

Vitis vinifera 'Pinot' clones were analysed at 50 microsatellite loci to assess intravarietal genetic diversity. When analysing leaf tissue DNAs, polymorphism mainly resulted from the appearance of a third allele when two were expected for heterozygous loci in a diploid species. The sequencing of the three microsatellite alleles at two loci has confirmed their simultaneous presence in the leaf tissues. A hypothesis explaining the triallelic profiles at a locus is the presence of a periclinal chimera meristem structure, in which genetically different cell layers coexist. The periclinal chimeric state of two Vitis vinifera 'Pinot gris' clones was confirmed by splitting and analysing the genotypes resulting from L1 and L2 cell layers in progeny derived from self-fertilization, in root tissues, and in plants regenerated from somatic embryogenesis. Prevalence of chimerism in polymorphic clones observed in a collection of 145 accessions belonging to 'Pinot gris', 'Pinot noir', Pinot blanc', 'Pinot meunier', and 'Pinot moure' cultivars was demonstrated. The accumulation of somatic mutations and cell layer rearrangements allowed us to deduce the relationships between the various genotypes and to open a way for understanding the diversification process and the phylogeny in the 'Pinot' group.