Exploiting Fast-Variables to Understand Population Dynamics and Evolution

We describe a continuous-time modelling framework for biological population dynamics that accounts for demographic noise. In the spirit of the methodology used by statistical physicists, transitions between the states of the system are caused by individual events while the dynamics are described in terms of the time-evolution of a probability density function. In general, the application of the diffusion approximation still leaves a description that is quite complex. However, in many biological applications one or more of the processes happen slowly relative to the system's other processes, and the dynamics can be approximated as occurring within a slow low-dimensional subspace. We review these time-scale separation arguments and analyse the more simple stochastic dynamics that result in a number of cases. We stress that it is important to retain the demographic noise derived in this way, and emphasise this point by showing that it can alter the direction of selection compared to the prediction made from an analysis of the corresponding deterministic model.Comment: 33 pages, 9 figure

Long-term changes in habitat and trophic level of Southern Ocean squid in relation to environmental conditions

Long-term studies of pelagic nekton in the Southern Ocean and their responses to ongoing environmental change are rare. Using stable isotope ratios measured in squid beaks recovered from diet samples of wandering albatrosses Diomedea exulans, we assessed decadal variation (from 1976 to 2016) in the habitat (δ13C) and trophic level (δ15N) of five important Southern Ocean squid species in relation to indices of environmental conditions—Southern Oscillation Index (SOI) and Southern Annular Mode (SAM). Based on δ13C values, corrected for the Suess effect, habitat had changed over the last 50 years for Taonius sp. B (Voss), Gonatus antarcticus, Galiteuthis glacialis and Histioteuthis atlantica but not Moroteuthopsis longimana. By comparison, mean δ15N values were similar across decades for all five species, suggesting minimal changes in trophic levels. Both SAM and SOI have increased in strength and frequency over the study period but, of the five species, only in Taonius sp. B (Voss) did these indices correlate with, δ13C and δ15N values, indicating direct relationships between environmental conditions, habitat and trophic level. The five cephalopod species therefore changed their habitats with changing environmental conditions over the last 50 years but maintained similar trophic levels. Hence, cephalopods are likely to remain important prey for top predators in Southern Ocean food webs, despite ongoing climate change

White Matter and Cognition in Adults Who Were Born Preterm

BACKGROUND AND PURPOSE: Individuals born very preterm (before 33 weeks of gestation, VPT) are at risk of damage to developing white matter, which may affect later cognition and behaviour. METHODS: We used diffusion tensor MRI (DT-MRI) to assess white matter microstructure (fractional anisotropy; FA) in 80 VPT and 41 term-born individuals (mean age 19.1 years, range 17-22, and 18.5 years, range 17-22 years, respectively). VPT individuals were part of a 1982-1984 birth cohort which had been followed up since birth; term individuals were recruited by local press advertisement. General intellectual function, executive function and memory were assessed. RESULTS: The VPT group had reduced FA in four clusters, and increased FA in four clusters relative to the Term group, involving several association tracts of both hemispheres. Clusters of increased FA were associated with more severe neonatal brain injury in the VPT group. Clusters of reduced FA were associated with lower birth weight and perinatal hypoxia, and with reduced adult cognitive performance in the VPT group only. CONCLUSIONS: Alterations of white matter microstructure persist into adulthood in VPT individuals and are associated with cognitive function

Cardiac resynchronization therapy guided by cardiovascular magnetic resonance

Cardiac resynchronization therapy (CRT) is an established treatment for patients with symptomatic heart failure, severely impaired left ventricular (LV) systolic dysfunction and a wide (> 120 ms) complex. As with any other treatment, the response to CRT is variable. The degree of pre-implant mechanical dyssynchrony, scar burden and scar localization to the vicinity of the LV pacing stimulus are known to influence response and outcome. In addition to its recognized role in the assessment of LV structure and function as well as myocardial scar, cardiovascular magnetic resonance (CMR) can be used to quantify global and regional LV dyssynchrony. This review focuses on the role of CMR in the assessment of patients undergoing CRT, with emphasis on risk stratification and LV lead deployment

Seizure prediction : ready for a new era

Acknowledgements: The authors acknowledge colleagues in the international seizure prediction group for valuable discussions. L.K. acknowledges funding support from the National Health and Medical Research Council (APP1130468) and the James S. McDonnell Foundation (220020419) and acknowledges the contribution of Dean R. Freestone at the University of Melbourne, Australia, to the creation of Fig. 3.Peer reviewedPostprin

Death, treatment decisions and the permanent vegetative state: evidence from families and experts

Some brain injured patients are left in a permanent vegetative state, i.e., they have irreversibly lost their capacity for consciousness but retained some autonomic physiological functions, such as breathing unaided. Having discussed the controversial nature of the permanent vegetative state as a diagnostic category, we turn to the question of the patients’ ontological status. Are the permanently vegetative alive, dead, or in some other state? We present empirical data from interviews with relatives of patients, and with experts, to support the view that the ontological state of permanently vegetative patients is unclear: such patients are neither straightforwardly alive nor simply dead. Having defended this view from counter-arguments we turn to the practical question as to how these patients ought to be treated. Some relatives and experts believe it is right for patients to be shifted from their currently unclear ontological state to that of being straightforwardly dead, but many are concerned or even horrified by the only legally sanctioned method guaranteed to achieve this, namely withdrawal of clinically assisted nutrition and hydration. A way of addressing this distress would be to allow active euthanasia for these patients. This is highly controversial; but we argue that standard objections to allowing active euthanasia for this particular class of permanently vegetative patients are weakened by these patients’ distinctive ontological status

Lack of long-term acclimation in Antarctic encrusting species suggests vulnerability to warming

Marine encrusting communities play vital roles in benthic ecosystems and have major economic implications with regards to biofouling. However, their ability to persist under projected warming scenarios remains poorly understood and is difficult to study under realistic conditions. Here, using heated settlement panel technologies, we show that after 18 months Antarctic encrusting communities do not acclimate to either +1 °C or +2 °C above ambient temperatures. There is significant up-regulation of the cellular stress response in warmed animals, their upper lethal temperatures decline with increasing ambient temperature and population genetic analyses show little evidence of differential survival of genotypes with treatment. By contrast, biofilm bacterial communities show no significant differences in community structure with temperature. Thus, metazoan and bacterial responses differ dramatically, suggesting that ecosystem responses to future climate change are likely to be far more complex than previously anticipated

Interstitial nephritis of unknown aetiology in captive slender‐horned gazelles ( Gazella leptoceros

Four captive slender-horned gazelles (Gazella leptoceros) died in a short period. The clinical signs were lethargy progressing rapidly to stupor and death. Differential diagnoses included trauma, intoxication, hepatic and renal failure. Blood analyses revealed increased blood urea nitrogen, creatinine, aspartate aminotransferase, alanine aminotransferase and creatine kinase. Serum mean copper levels had risen almost two-fold. No trauma was found and salient post-mortem examination results were friable livers and granular and/or pitted renal capsular surfaces with indentations. The most consistent histological change was chronic interstitial lymphoplasmacytic nephritis, tubular degeneration and glomerulosclerosis. Potential causes were investigated and ruled out. Erysipelothrix rhusiopathiae was cultured from the liver and the kidney of three animals, but could not be confirmed histopathologically. Polymerase chain reaction (PCR) carried out on kidney and liver and serological screening were negative for leptospirosis. Copper involvement could not be confirmed by toxicological analysis of liver and kidney tissue or by histopathology. The aetiology remains unknown