New parasites and predators follow the introduction of two fish species to a subarctic lake: implications for food-web structure and functioning

Introduced species can alter the topology of food webs. For instance, an introduction can aid the arrival of free-living consumers using the new species as a resource, while new parasites may also arrive with the introduced species. Food-web responses to species additions can thus be far more complex than anticipated. In a subarctic pelagic food web with free-living and parasitic species, two fish species (arctic charr Salvelinus alpinus and three-spined stickleback Gasterosteus aculeatus) have known histories as deliberate introductions. The effects of these introductions on the food web were explored by comparing the current pelagic web with a heuristic reconstruction of the pre-introduction web. Extinctions caused by these introductions could not be evaluated by this approach. The introduced fish species have become important hubs in the trophic network, interacting with numerous parasites, predators and prey. In particular, five parasite species and four predatory bird species depend on the two introduced species as obligate trophic resources in the pelagic web and could therefore not have been present in the pre-introduction network. The presence of the two introduced fish species and the arrival of their associated parasites and predators increased biodiversity, mean trophic level, linkage density, and nestedness; altering both the network structure and functioning of the pelagic web. Parasites, in particular trophically transmitted species, had a prominent role in the network alterations that followed the introductions.     

Alexander Böhm (1971–2012)

On November 28, 2012 Alexander (Alex) Böhm, a bacterial geneticist, died at age 41, only a few months after taking up a position as an assistant professor at the LOEWE Center for Synthetic Microbiology in Marburg, Germany. Earlier in 2012 Alex had been diagnosed with an aggressive form of thyroid cancer that left him little time to live his scientific and personal dreams.     

Pediatric Invasive Pneumococcal Disease Caused by Vaccine Serotypes following the Introduction of Conjugate Vaccination in Denmark

A seven-valent pneumococcal conjugate vaccine (PCV7) was introduced in the Danish childhood immunization program (2+1 schedule) in October 2007, followed by PCV13 starting from April 2010. The nationwide incidence of IPD among children younger than 5 years nearly halved after the introduction of PCV7 in the program, mainly due to a decline in IPD caused by PCV7-serotypes. We report the results from a nationwide population-based cohort study of laboratory confirmed IPD cases in children younger than 5 years during October 1, 2007 to December 31, 2010 and describe the characteristics of children suspected to present with a vaccine failure. The period between April 19 and December 31, 2010 was considered a PCV7/PCV13 transitional period, where both vaccines were offered. We identified 45 episodes of IPD caused by a PCV7 serotype (23% of the total number) and 105 (55%) caused by one of the 6 additional serotypes in PCV13. Ten children had received at least one PCV7 dose before the onset of IPD caused by a PCV7 serotype. Seven children were considered to be incompletely vaccinated before IPD, but only three cases fulfilled the criteria of vaccine failure (caused by serotypes 14, 19F and 23F). One case of vaccine failure was observed in a severely immunosuppressed child following three PCV7 doses, and two cases were observed in immunocompetent children following two infant doses before they were eligible for their booster. None of the IPD cases caused by the additional PCV13 serotypes had been vaccinated by PCV13 and there were therefore no PCV13-vaccine failures in the first 8-months after PCV13 introduction in Denmark.     

Characteristics of rapid eye movement sleep behavior disorder in narcolepsy

The basal forebrain (BF) plays an important role in regulating cortical activity and sleep/wake states. Both cholinergic and non-cholinergic neurons of the BF project to the cerebral cortex and hippocampus, whereas the hypothalamus and brainstem nuclei are mostly innervated by non-cholinergic BF neurons. Neurons in the BF show various discharge profiles in relation to cortical activity and behavioral states and are differentially modulated by neurotransmitters of other sleep/wake regulatory neurons. Recent technical advances have made it possible to correlate discharge profiles of single BF neurons during sleep/wake states with their neurochemical phenotypes, and to make selective lesions of certain cell types. The goal of this review is to summarize the current knowledge of the anatomy and sleep/wake regulatory functions of cholinergic and non-cholinergic BF neurons. We will first review the anatomical heterogeneity of BF neurons, and then discuss recent evidence for the firing patterns of BF cholinergic and non-cholinergic neurons during natural sleep–wake patterns, and finally, discuss their roles in sleep homeostasis. It is proposed that through different neurotransmitters, projections, and state-regulated activity, the cholinergic and non-cholinergic BF neurons collectively and differently regulate cortical activity and sleep-wake states.

     

Glutamine Metabolism Regulates Proliferation and Lineage Allocation in Skeletal Stem Cells

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Incorporating experimental design and error into coalescent/mutation models of population history

Coalescent theory provides a powerful framework for estimating the evolutionary, demographic, and genetic parameters of a population from a small sample of individuals. Current coalescent models have largely focused on population genetic factors (e.g., mutation, population growth, and migration) rather than on the effects of experimental design and error. This study develops a new coalescent/mutation model that accounts for unobserved polymorphisms due to missing data, sequence errors, and multiple reads for diploid individuals. The importance of accommodating these effects of experimental design and error is illustrated with evolutionary simulations and a real data set from a population of the California sea hare. In particular, a failure to account for sequence errors can lead to overestimated mutation rates, inflated coalescent times, and inappropriate conclusions about the population. This current model can now serve as a starting point for the development of newer models with additional experimental and population genetic factors. It is currently implemented as a maximum-likelihood method, but this model may also serve as the basis for the development of Bayesian approaches that incorporate experimental design and error.     

Adipose tissue interleukin-18 mRNA and plasma interleukin-18: effect of obesity and exercise

Objectives: Obesity and a physically inactive lifestyle are associated with increased risk of developing insulin resistance. The hypothesis that obesity is associated with increased adipose tissue (AT) interleukin (IL)‐18 mRNA expression and that AT IL‐18 mRNA expression is related to insulin resistance was tested. Furthermore, we speculated that acute exercise and exercise training would regulate AT IL‐18 mRNA expression. Research Methods and Procedures: Non‐obese subjects with BMI < 30 kg/m² (women: n = 18; men; n = 11) and obese subjects with BMI >30 kg/m² (women: n = 6; men: n = 7) participated in the study. Blood samples and abdominal subcutaneous AT biopsies were obtained at rest, immediately after an acute exercise bout, and at 2 hours or 10 hours of recovery. After 8 weeks of exercise training of the obese group, sampling was repeated 48 hours after the last training session. Results: AT IL‐18 mRNA content and plasma IL‐18 concentration were higher (p < 0.05) in the obese group than in the non‐obese group. AT IL‐18 mRNA content and plasma IL‐18 concentration was positively correlated (p < 0.05) with insulin resistance. While acute exercise did not affect IL‐18 mRNA expression at the studied time‐points, exercise training reduced AT IL‐18 mRNA content by 20% in both sexes. Discussion: Because obesity and insulin resistance were associated with elevated AT IL‐18 mRNA and plasma IL‐18 levels, the training‐induced lowering of AT IL‐18 mRNA content may contribute to the beneficial effects of regular physical activity with improved insulin sensitivity.     

Introduction of Mysis relicta (Mysida) reduces niche segregation between deep-water Arctic charr morphs

Hydrobiologia - Understanding the concordance between aquatic assemblages in ecological assessments and their responses to human-induced disturbances are fundamental steps toward achieving...     

Contrasting patterns in trophic niche evolution of polymorphic Arctic charr populations in two subarctic Norwegian lakes

Hydrobiologia - Lipid biomarkers in sediments, which are indicative of biological production, provide important information regarding the environmental conditions in and around lakes, and can be...