Sexual selection on land snail shell ornamentation: a hypothesis that may explain shell diversity

Background  

Many groups of land snails show great interspecific diversity in shell ornamentation, which may include spines on the shell and flanges on the aperture. Such structures have been explained as camouflage or defence, but the possibility that they might be under sexual selection has not previously been explored.     

Dualism and conflicts in understanding speciation

Speciation is a central but elusive issue in evolutionary biology. Over the past sixty years, the subject has been studied within a framework conceived by Ernst Mayr and Theodosius Dobzhansky and subsequently developed further by numerous other workers. In this "isolation" theory, the evolution of reproductive isolation is a key element of speciation; natural selection is given only secondary importance while gene flow is considered prohibitive to the process. In this paper, I argue that certain elements in this approach have produced confusion and irreconcilability among students of speciation. The more prominent debates in speciation (i.e., the species definition, sympatry/allopatry, and the role of reinforcement) all derive from an inherent conflict between the "isolation" theory and Darwin's "selection" view on species and speciation (in which disruptive selection is crucial). New data, mainly from field ecology, molecular population genetics, laboratory studies with Drosophila and computer analysis, all suggest that the isolation theory may no longer be the most desirable vantage point from which to explore speciation. Instead, environmental selection in large populations, often unimpeded by ongoing gene flow, appears to be the decisive element. The traditional preoccupation with reproductive isolation has created gaps in our knowledge of several crucial issues, mainly regarding the role of environmental selection and its connection with mate selection.     

Comparison of Perceived and Technical Healthcare Quality in Primary Health Facilities: Implications for a Sustainable National Health Insurance Scheme in Ghana

Background

Quality care in health facilities is critical for a sustainable health insurance system because of its influence on clients’ decisions to participate in health insurance and utilize health services. Exploration of the different dimensions of healthcare quality and their associations will help determine more effective quality improvement interventions and health insurance sustainability strategies, especially in resource constrained countries in Africa where universal access to good quality care remains a challenge.

Purpose

To examine the differences in perceptions of clients and health staff on quality healthcare and determine if these perceptions are associated with technical quality proxies in health facilities. Implications of the findings for a sustainable National Health Insurance Scheme (NHIS) in Ghana are also discussed.

Methods

This is a cross-sectional study in two southern regions in Ghana involving 64 primary health facilities: 1,903 households and 324 health staff. Data collection lasted from March to June, 2012. A Wilcoxon-Mann-Whitney test was performed to determine differences in client and health staff perceptions of quality healthcare. Spearman’s rank correlation test was used to ascertain associations between perceived and technical quality care proxies in health facilities, and ordered logistic regression employed to predict the determinants of client and staff-perceived quality healthcare.

Results

Negative association was found between technical quality and client-perceived quality care (coef. = -0.0991, p<0.0001). Significant staff-client perception differences were found in all healthcare quality proxies, suggesting some level of unbalanced commitment to quality improvement and potential information asymmetry between clients and service providers. Overall, the findings suggest that increased efforts towards technical quality care alone will not necessarily translate into better client-perceived quality care and willingness to utilize health services in NHIS-accredited health facilities.

Conclusion

There is the need to intensify client education and balanced commitment to technical and perceived quality improvement efforts. This will help enhance client confidence in Ghana’s healthcare system, stimulate active participation in the national health insurance, increase healthcare utilization and ultimately improve public health outcomes.     

The HAS-BLED Score Identifies Patients with Acute Venous Thromboembolism at High Risk of Major Bleeding Complications during the First Six Months of Anticoagulant Treatment

Objective

The HAS-BLED score enables a risk estimate of major bleeds in patients with atrial fibrillation on vitamin K-antagonists (VKA) treatment, but has not been validated for patients with venous thromboembolism (VTE). We analyzed whether the HAS-BLED score accurately identifies patients at high risk of major bleeds during VKA treatment for acute VTE.

Methods

Medical records of 537 patients with acute VTE (primary diagnosis pulmonary embolism in 223, deep vein thrombosis in 314) starting VKA treatment between 2006-2007 were searched for items on the HAS-BLED score and the occurrence of major bleeds during the first 180 days of follow-up. The hazard ratio (HR) for the occurrence of major bleeds comparing non-high with high-risk patients as defined by a HAS-BLED score ≥ 3 points was calculated using Cox-regression analysis.

Results

Major bleeds occurred in 11/537 patients (2.0%, 5.2/100 person years, 95% CI 2.8-9.2). Cumulative incidences of major bleeds were 1.3% (95% CI 0.1-2.5) in the non-high (HAS-BLED < 3) and 9.6% (95%CI 2.2-17.0) in the high-risk group (HAS-BLED ≥ 3), (p <0.0001 by Log-Rank test), with a HR of 8.7 (95% CI 2.7-28.4). Of the items in the HAS-BLED score, abnormal renal function (HR 10.8, 95% CI 1.9-61.7) and a history of bleeding events (HR 10.4, 95% CI 2.5-42.5) were independent predictors of major bleeds during follow-up.

Conclusion

Acute VTE patients with a HAS-BLED score ≥ 3 points are at increased risk of major bleeding. These results warrant for correction of the potentially reversible risk factors for major bleeding and careful International Normalized Ratio monitoring in acute VTE patients with a high HAS-BLED score.     

Decreased Memory B Cells and Increased CD8 Memory T Cells in Blood of Breastfed Children: The Generation R Study

BackgroundBreastfeeding provides a protective effect against infectious diseases in infancy. Still, immunological evidence for enhanced adaptive immunity in breastfed children remains inconclusive.ObjectiveTo determine whether breastfeeding affects B- and T-cell memory in the first years of life.MethodsWe performed immunophenotypic analysis on blood samples within a population-based prospective cohort study. Participants included children at 6 months (n=258), 14 months (n=166), 25 months (n=112) and 6 years of age (n=332) with both data on breastfeeding and blood lymphocytes. Total B- and T-cell numbers and their memory subsets were determined with 6-color flow cytometry. Mothers completed questionnaires on breastfeeding when their children were aged 2, 6, and 12 months. Multiple linear regression models with adjustments for potential confounders were performed.ResultsPer month continuation of breastfeeding, a 3% (95% CI -6, -1) decrease in CD27+IgM+, a 2% (95 CI % -5, -1) decrease in CD27+IgA+ and a 2% (95% CI -4, -1) decrease in CD27-IgG+ memory B cell numbers were observed at 6 months of age. CD8 T-cell numbers at 6 months of age were 20% (95% CI 3, 37) higher in breastfed than in non-breastfed infants. This was mainly found for central memory CD8 T cells and associated with exposure to breast milk, rather than duration. The same trend was observed at 14 months, but associations disappeared at older ages.ConclusionsLonger breastfeeding is associated with increased CD8 T-cell memory, but not B-cell memory numbers in the first 6 months of life. This transient skewing towards T cell memory might contribute to the protective effect against infectious diseases in infancy.     

Extracellular ATP triggers and maintains asthmatic airway inflammation by activating dendritic cells

Extracellular ATP serves as a danger signal to alert the immune system of tissue damage by acting on P2X or P2Y receptors. Here we show that allergen challenge causes acute accumulation of ATP in the airways of asthmatic subjects and mice with experimentally induced asthma. All the cardinal features of asthma, including eosinophilic airway inflammation, Th2 cytokine production and bronchial hyper-reactivity, were abrogated when lung ATP levels were locally neutralized using apyrase or when mice were treated with broad-spectrum P2-receptor antagonists. In addition to these effects of ATP in established inflammation, Th2 sensitization to inhaled antigen was enhanced by endogenous or exogenous ATP. The adjuvant effects of ATP were due to the recruitment and activation of lung myeloid dendritic cells that induced Th2 responses in the mediastinal nodes. Together these data show that purinergic signaling has a key role in allergen-driven lung inflammation that is likely to be amenable to therapeutic intervention.     

Reprogramming factor stoichiometry influences the epigenetic state and biological properties of induced pluripotent stem cells

We compared two genetically highly defined transgenic systems to identify parameters affecting reprogramming of somatic cells to a pluripotent state. Our results demonstrate that the level and stoichiometry of reprogramming factors during the reprogramming process strongly influence the resulting pluripotency of iPS cells. High expression of Oct4 and Klf4 combined with lower expression of c-Myc and Sox2 produced iPS cells that efficiently generated "all-iPSC mice" by tetraploid (4n) complementation, maintained normal imprinting at the Dlk1-Dio3 locus, and did not create mice with tumors. Loss of imprinting (LOI) at the Dlk1-Dio3 locus did not strictly correlate with reduced pluripotency though the efficiency of generating "all-iPSC mice" was diminished. Our data indicate that stoichiometry of reprogramming factors can influence epigenetic and biological properties of iPS cells. This concept complicates efforts to define a "generic" epigenetic state of iPSCs and ESCs and should be considered when comparing different iPS and ES cell lines.