Modeling pN2 through Geological Time: Implications for Planetary Climates and Atmospheric Biosignatures

Nitrogen is a major nutrient for all life on Earth and could plausibly play a similar role in extraterrestrial biospheres. The major reservoir of nitrogen at Earth's surface is atmospheric N₂, but recent studies have proposed that the size of this reservoir may have fluctuated significantly over the course of Earth's history with particularly low levels in the Neoarchean-presumably as a result of biological activity. We used a biogeochemical box model to test which conditions are necessary to cause large swings in atmospheric N₂ pressure. Parameters for our model are constrained by observations of modern Earth and reconstructions of biomass burial and oxidative weathering in deep time. A 1-D climate model was used to model potential effects on atmospheric climate. In a second set of tests, we perturbed our box model to investigate which parameters have the greatest impact on the evolution of atmospheric pN₂ and consider possible implications for nitrogen cycling on other planets. Our results suggest that (a) a high rate of biomass burial would have been needed in the Archean to draw down atmospheric pN₂ to less than half modern levels, (b) the resulting effect on temperature could probably have been compensated by increasing solar luminosity and a mild increase in pCO₂, and (c) atmospheric oxygenation could have initiated a stepwise pN₂ rebound through oxidative weathering. In general, life appears to be necessary for significant atmospheric pN₂ swings on Earth-like planets. Our results further support the idea that an exoplanetary atmosphere rich in both N₂ and O₂ is a signature of an oxygen-producing biosphere. Key Words: Biosignatures-Early Earth-Planetary atmospheres. Astrobiology 16, 949-963.

Boundary crossing for moving sums

Let Xi, i ≧ 1, be a sequence of independent N(0, 1) random variables and Sj,m = Xj + · ·· + Xj+m–1, the jth moving sum. Let τ m = inf{j ≧ 1 : Sj,m > a} + m – 1, the boundary crossing time. Approximation in the spirit of Glaz and Johnson (1984), (1986) and Samuel-Cahn (1983) are given for Pr(τm > n), E(τ m), and σ (τ m),the standard deviation of τm.

The Rapidly Acting Antidepressant Ketamine and the mGlu2/3 Receptor Antagonist LY341495 Rapidly Engage Dopaminergic Mood Circuits

Ketamine is a rapidly acting antidepressant in patients with treatment-resistant depression (TRD). Although the mechanisms underlying these effects are not fully established, inquiry to date has focused on the triggering of synaptogenesis transduction pathways via glutamatergic mechanisms. Preclinical data suggest that blockade of metabotropic glutamate (mGlu2/3) receptors shares many overlapping features and mechanisms with ketamine and may also provide rapid efficacy for TRD patients. Central dopamine circuitry is recognized as an end target for mood regulation and hedonic valuation and yet has been largely neglected in mechanistic studies of antidepressant-relevant effects of ketamine. Herein, we evaluated the changes in dopaminergic neurotransmission after acute administration of ketamine and the mGlu2/3 receptor antagonist LY341495 [(2S)-2-amino-2-[(1S,2S)-2-carboxycycloprop-1-yl]-3-(xanth-9-yl) propanoic acid ] in preclinical models using electrophysiologic, neurochemical, and behavioral endpoints. When given acutely, both ketamine and LY341495, but not the selective serotonin reuptake inhibitor (SSRI) citalopram, increased the number of spontaneously active dopamine neurons in the ventral tegmental area (VTA), increased extracellular levels of dopamine in the nucleus accumbens and prefrontal cortex, and enhanced the locomotor stimulatory effects of the dopamine D2/3 receptor agonist quinpirole. Further, both ketamine and LY341495 reduced immobility time in the tail-suspension assay in CD1 mice, which are relatively resistant to SSRI antidepressants. Both the VTA neuronal activation and the antidepressant phenotype induced by ketamine and LY341495 were attenuated by the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo- (9CI)-benzo[f]quinoxaline-7-sulfonamide, indicating AMPA-dependent effects. These findings provide another overlapping mechanism of action of ketamine and mGlu2/3 receptor antagonism that differentiates them from conventional antidepressants and thus support the potential rapidly acting antidepressant actions of mGlu2/3 receptor antagonism in patients.

Nesting sites in agricultural landscapes may reduce the reproductive success of populations of Blanding’s Turtles (Emydoidea blandingii)

Almost all turtle species nest in terrestrial environments and maternal site selection represents a critical component of nest success. Females use cues in the current environment to predict the future conditions for embryo development. However, in disturbed landscapes, current and future conditions may not be correlated. We compared selection of nest sites by Blanding’s Turtles (Emydoidea blandingii (Holbrook, 1838)) in a (relatively undisturbed) park and a (heavily disturbed) agricultural landscape in Ontario, Canada, using field measurements and satellite imagery. Environmental variables were compared using logistic regression and Akaike’s information criterion (AIC) based on data measured at nest (presence) and random (pseudoabsence) locations. Specific environmental variables associated with site selection differed between study areas. Most notably, NDVI (normalized difference vegetation index, a proxy for vegetation cover) increased significantly during the year at the agricultural locale, corresponding with the growth of planted fields. No parallel change was observed at the park locale where canopy cover remained more consistent. An increase in vegetation cover may alter nest temperatures and soil moisture. Combined with the unpredictability in timing of crop sowing and harvesting, findings suggest that nests in agricultural fields may act as ecological sinks and that other species nesting in similarly altered habitats may be subjected to the same threats.

Treatment of Disseminated Aspergillosis with Posaconazole in 10 Dogs

Background

Few effective treatments for disseminated Aspergillus infections in dogs are available. Posaconazole has potent and broad‐spectrum activity against Aspergillus spp., but its use has not yet been sufficiently evaluated in dogs.

Hypothesis/Objectives

The aim of this study was to determine the safety and efficacy of posaconazole for the treatment of naturally occurring disseminated Aspergillus infections in dogs.

Animals

Ten client‐owned dogs with disseminated aspergillosis.

Methods

Prospective, nonrandomized, noncontrolled study with posaconazole administered to dogs at dosage of 5 mg/kg PO q12h. The primary veterinarian or the veterinary specialist caring for the dogs provided patient data.

Results

The treatment response for dogs with disseminated disease while receiving posaconazole was defined as clinical remission (n = 4) and clinical improvement (n = 6). There was a high rate of relapse during treatment or after cessation of treatment in both groups, and most dogs died or were euthanized due to progressive disease. Excluding 1 dog concurrently treated with terbinafine that remains alive 5 years after diagnosis, the mean survival time for dogs was 241 days (range 44–516 days). Three other dogs lived >1 year after starting treatment. No clinically relevant adverse events or increases in serum liver enzyme activity occurred during treatment with posaconazole.

Conclusions and Clinical Importance

Posaconazole appears to be safe and well‐tolerated for treatment of disseminated Aspergillus infections in dogs. Long‐term survival >1 year is possible with prolonged treatment, but relapse is common.

Health workforce planning and service expansion during an economic crisis: A case study of the national breast screening programme in Ireland

This article aims to estimate the workforce and resource implications of the proposed age extension of the national breast screening programme, under the economic constraints of reduced health budgets and staffing levels in the Irish health system. Using a mixed method design, a purposive sample of 20 participants were interviewed and data were analysed thematically (June-September 2012). Quantitative data (programme-level activity data, screening activity, staffing levels and screening plans) were used to model potential workload and resource requirements. The analysis indicates that over 90% operational efficiency was achieved throughout the first six months of 2012. Accounting for maternity leave (10%) and sick leave (3.5%), 16.1 additional radiographers (whole time equivalent) would be required for the workload created by the age extension of the screening programme, at 90% operational efficiency. The results suggest that service expansion is possible with relatively minimal additional radiography resources if the efficiency of the skill mix and the use of equipment are improved. Investing in the appropriate skill mix should not be limited to clinical groups but should also include administrative staff to manage and support the service. Workload modelling may contribute to improved health workforce planning and service efficiency.

Schizophrenia through the carers' eyes: results of a European cross-sectional survey

Schizophrenia is a serious mental disorder affecting approximately 29 million people worldwide. The ideal treatment and care of patients with schizophrenia should be provided by a multidisciplinary 'team' involving psychiatrists, nurses and other healthcare professionals, together with carers and patients. In light of the key role carers play in the care of patients with schizophrenia, the present survey was designed to assess the opinions of family members and friends of patients with schizophrenia across Europe and to ascertain their attitudes towards the illness, medication and adherence to medication. Among carers participating in this survey, there was widespread awareness of the issues involved in supporting patients with schizophrenia and the importance of their role in improving poor adherence to medication. Three differences in opinion emerged between the views of carers and psychiatrists; psychiatrists rely more on the patient themselves when assessing adherence than carers would recommend; in contrast to psychiatrists, many carers believe the illness itself contributes to non-adherence; two thirds of carers think that schizophrenia medication damages health (higher than estimated by psychiatrists). The findings from the present survey, taken together with the results from the Adherencia Terapéutica en la Esquizofrenia surveys of psychiatrists and nurses, support the need for a collaborative approach to the issue of treatment nonadherence. In particular, healthcare professionals should recognize the valuable contribution that family carers can make to improve treatment adherence and consequently clinical outcomes for patients with schizophrenia. Schizophrenia carries a significant burden for families providing care. The Adherencia Terapéutica en la Esquizofrenia (ADHES) carers' survey was designed to assess the opinions of family and friends of patients with schizophrenia across Europe and ascertain their attitudes towards the illness, medication and adherence to medication. A questionnaire-based cross-sectional survey of 138 carers across 16 European countries. Interpretation of results was based on a descriptive comparison of responses. Carers recognized the importance of medication to help patients get better (76%) and improve their quality of life (76%) and relationships (74%). Sixty-seven per cent believed medication damages general health. Sixty-five per cent reported that treatment adherence was a burden for patients. Thirty-eight per cent indicated that it was a daily struggle to get patients to take their medication. Fifty per cent perceived that medication administered every few weeks rather than daily was quite/very important. Ninety-three per cent agreed on the importance of family support to boost adherence, with education and information deemed important for families and patients. Carers rely less on the patient themselves when assessing adherence than psychiatrists. The burden faced by carers and patients in taking medication provides an opportunity for healthcare professionals to provide support in a multidisciplinary 'team' involving psychiatrists, nurses and carers.

The molecular genetic architecture of attention deficit hyperactivity disorder

Attention deficit hyperactivity disorder (ADHD) is a common childhood behavioral condition which affects 2-10% of school age children worldwide. Although the underlying molecular mechanism for the disorder is poorly understood, familial, twin and adoption studies suggest a strong genetic component. Here we provide a state-of-the-art review of the molecular genetics of ADHD incorporating evidence from candidate gene and linkage designs, as well as genome-wide association (GWA) studies of common single-nucleotide polymorphisms (SNPs) and rare copy number variations (CNVs). Bioinformatic methods such as functional enrichment analysis and protein-protein network analysis are used to highlight biological processes of likely relevance to the aetiology of ADHD. Candidate gene associations of minor effect size have been replicated across a number of genes including SLC6A3, DRD5, DRD4, SLC6A4, LPHN3, SNAP-25, HTR1B, NOS1 and GIT1. Although case-control SNP-GWAS have had limited success in identifying common genetic variants for ADHD that surpass critical significance thresholds, quantitative trait designs suggest promising associations with Cadherin13 and glucose-fructose oxidoreductase domain 1 genes. Further, CNVs mapped to glutamate receptor genes (GRM1, GRM5, GRM7 and GRM8) have been implicated in the aetiology of the disorder and overlap with bioinformatic predictions based on ADHD GWAS SNP data regarding enriched pathways. Although increases in sample size across multi-center cohorts will likely yield important new results, we advocate that this must occur in parallel with a shift away from categorical case-control approaches that view ADHD as a unitary construct, towards dimensional approaches that incorporate endophenotypes and statistical classification methods.